I am deeply saddened and disturbed that you actually believe the Korean War was a "fight for democracy". When the North "invaded" the South they were trying to kick out the foreign powers who'd captured Korea from the Japanese then divided it up amongst themselves to perform what can only be described as a sick social experiment to play communism off against capitalism. The original plan was to reunite Korea and see which side had the "superior" ideology. When this was abandoned the North took matters into their own hands.
I recently ran into someone in another subreddit who made this assertion, and would like to hear the conclusions of people who have thoroughly studied the matter.
The typical narrative in Western circles is that the UN (US) Forces were acting to preserve the independence of South Korea against unwarranted and unprovoked North Korean communist invasion in the aftermath of the free elections, and that the USSR and North Koreans were acting in bad faith prior to the invasion. Critics would argue this narrative ignores the re-establishment of former Japanese bureaucratic machines by the USAMGIK and RoK, the repression of Koreans by the South/ US (though in fairness it seems far more difficult to accurately gauge Occupation period repression in the north), and the decision to violate the Moscow Conference and hold free elections. (Which in both countries seemed to be rather dubious).
On the other side of the fence, it seems well accepted that Kim-Il Sung was hand picked by the Soviets to act as a proxy for their agenda in the region after the failure of homegrown communist movements to gain traction. Land reform and the events of the soviet occupation caused around half a million North Koreans to flee south, though some sources indicate this was relatively "bloodless", and evidence seems to suggest Kim wanted war as early as 1948 to reunify the peninsula, only held off by Stalin's desire to withdraw beforehand. (does that mean the Russians saw SK as illegitimate or was it a pure power grab?). NK seemed to have viewed the conflict as a means of forcing out foreign occupation and liberating the peninsula from the vestiges of imperialism (and the remnants of the Japanese occupation).
So how exactly should the war be classified? As an attempt to preserve the independence of South Korea against unwarranted aggression from North Korea? A conflict to liberate the South from new foreign occupation, residual Japanese collaborator influence, and end foreign imperialism? Or a ideological war between the West and the USSR?
I think a better question would be why do you think the Korean War needs a single master narrative?
The critiques of each version of a master narrative that you have already laid out are all valid, but the narratives also have grains of truth. Professional historians without a nationalist dog in the fight usually argue against the simple narratives and try to get people to understand the complexities and ambivalence of all parties involved. Almost any punchy one liner that sums up the war is going to wrong by virtue of oversimplification, so why not embrace the ambivalence?
If I had to try to put a bow on it, I would say that the Korean War was a tragic conflict resulting from multilayered tensions stemming both from Japanese imperialism and earlier Korean domestic conflicts, loosely organized along (and exacerbated by) the lines of an arbitrary division by ideologically opposed powers with more interest in their regional influence than Korean self determination and unity. Korean leaders on both sides believed in a united Korea, but thought they should be the ones in control of it. War broke out after numerous back and forth border skirmishes, and leaders on both sides presented their cases in terms that would win them backing from ideological allies.
In the end it was all and none of those things, and that's not a problem. It's more important to understand the causes and the consequences of both the war itself and the narratives about it than it is to make a final judgement.
The water downstream will not be clear if the upstream water is muddy. Korean proverb
There have been three wars fought on the Korean peninsula in modern times. Each time foreign powers fought for their own interests and each time it was the Korean people who suffered. Again and again Korea has suffered war without gaining anything for its suffering. Korea is suffering still. Korea is and has been a breeding ground for conflict for three reasons; location, location, location.
For anyone not Korean, the poor, dusty, impoverished, filthy mountainous land in Korea with its harsh climate is not worth fighting and dying over. For the early Manchu invaders, and later the rising Empire of Japan, the vast and rich land in Manchuria was always the prize, the Korean borderlands were just the road to get there or the buffer to keep others out.
With eyes on this prize, Japanese troops invaded, met and defeated the Manchu army near Pyongyang. With victory, Japan forced the Treaty of Shimonoseki on the parties involved on 17 April 1895. For its troubles, the Empire took Taiwan while the Manchu rulers ceded Korea.
Whoever wants control of Manchuria necessarily must own Korea. Russia, always hungry for land, moved into the Manchurian void left as the defeated, dying Manchu dynasty's power faded. This put Russia interests in direct competition with Japan. By 1904, Japan and czarist Russia went to war over the region. Imperial Japanese troops landed at Inchon, near Seoul, marched north across the Yalu River, and soundly whipped the Imperial Russians. Japan won the battle and won the war with material aid supplied by United States and Great Britain, two nations which had watched the Russian advance to the Pacific Ocean with fear and loathing.
Japan ruled Korea harshly until the Empire's cruel heart was finally burned out by American airpower and atomic bombs in 1945.
As soon as logistically possible after Japan's surrender, a 120,000 man Soviet army crossed the Yalu into Korea and marched south. The Americans, enjoying their recent victory, and focused on occupying Japan, were slow to react. Before the Russians could take the entire country, however, it was agreed US would take control of the land south of the 38th parallel and leave the parts north to the Soviets.
Five years later, Soviet T-34 tanks crossed the parallel with Soviet trucks and Soviet-trained Korean troops shooting Soviet guns. The sudden violence of the surpise invasion caught President Truman vacationing in Independence, Mo. While America was enjoying peace, the Soviets had prepared their client state for war. The Russians had had different ideas about what needed to be done about the Korean problem. The Russians knew, as the Americans failed to understand, that Communist control of the peninsula would be disastrous for America's interests and prestige in Japan. Considering American incompetence and unpreparedness, it looked like a sure thing to Stalin and he went for it. The Soviet planned invasion was naked aggression with rational goals.
American strategic interests required a response. Communist expansion was to be opposed. Truman decided United States would fight as soon as he heard the news of the invasion.
America, with the UN's blessing and token assistance, held the line in the south, just barely. Once the tide turned, some saw an opportunity for the allies to liberate North Korea from the tyranny of Communist dictatorship. The Communist Chinese army crossed the Yalu in the 100's of thousands and soon put shut to that attempt.
"This Kind of War, the Classic Korean War History," T.R. Fehrenbach
North Korea was always, as it is today, a bad place to live. The Communist leadership took its style of nasty repression from the sadistic Stalinist model. South Korea wasn't a liberal European-style democracy, but it was always better than the rule of Kim. Today, the contrast between the two parts is stark. It is difficult to argue moral equivalence given the facts on the ground. North Korea invaded as a Soviet proxy, America defended the South for its national interests but those interests always include a moral component. United States didn't want to rule Korea. American soldiers, sailors, Marines and airmen were fighting and dying to stop Communist aggression, not to gain territory. The war no doubt spiraled out of the control of the political leadership on all sides with unforeseen consequences, but America didn't start it.
There is a common phrase, "history is written by the victor". Definitely in the US we have a narrative for the conflict just like they do in N. Korea. In this case it is a difficult question to answer. I'm no expert on Korean politics but depending on your point of view all of those interpretations are valid. The truth lies somewhere in between.
Did Kim Il Sung see himself as a liberator of Korea? Yes, and so did Syngman Rhee in the south.
We do know that the powers that be in the south opposed the american/soviet trusteeship and wanted all foreign influence out of Korea. The split of Korea into North and South went against earlier agreements and excluded the Koreans from talks. At this early stage it was definitely political maneuvering.
Were the Russians and US trying to fight a proxy war over capitalism v communism. You bet. You only have to look at the actions by both sides and the statements made by figures such as MacArthur to see that.
I will make a note of saying that opinion was split in the US command over what the goals and purpose of the Korean conflict was about. You had the diehards like MacArthur who did want to wipe out communism and who actively argued for taking the war into China as well as using nukes. You also had people like President Truman and Eisenhower who wanted to contain the conflict to the Korean peninsula.
When you get into the discussion of proxy war versus imperialism and freedom it gets very murky as it is all those things at once. There is the underlying belief on both sides that their ideology is right and they are fighting for freedom, but you cannot discount the possible political and economic benefits to having other countries align with your world view and of course every victory for you is a set back for the other guy.
I know it's not the answer you were looking for and depending on which historian you read you will get a different answer as there are leftist, neocon and revisionist works all concerning this but I think the truth lies somewhere in the grey on this one. It makes it even harder to judge when in the long run S. Korea has flourished whereas N. Korea has not. It's not such a clear picture like in Vietnam where everyone agrees the US were there for all the wrong reasons and didn't achieve much.
EDIT: forgot to add in the perspective of the southern koreans