claiming the lives of millions of people and all for nothing really.

The changes WWI caused were vast. Advances in medicine and technology, changes in the attitude of the lower classes to the upper both on and off the battlefield, changes in housing and unemployment, changes of government, the list is enormous. Entirely new countries were created. It also, arguably, seeded further conflict. Not quite 'nothing', rather, a lot of somethings.

seems like a war that was completely unjustifiable

All of it? Even those defending against invasion?

and the Generals of both sides seemed very incompetent and ruthless with their own men.

Blatantly false. The myth of the officer sitting safely well behind the lines while men died is just that. The British lost more senior officers to small arms and shell fire in WWI than WWII, for instance. The sheer amount of men killed was thanks to advances in firepower that were not matched by advances in mobility and communications.

They didn't seem to give a damn about the pawn sitting in the trenches surrounded by death, waiting to die and starving.

This is certainly the bad fiction version of WWI, yes. Here is a great comment about what daily life was actually like. The rest of the thread provides more detail.

So was WW1 pointless in your opinion?

No. WWI had a great many consequences. To say it was "all for nothing" is simply not true.

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I am generalising here, but the Pre-war mentality was that was war necessary and inevitable. Not necessarily such a large war, but definitely some wars.

Since the 1870s the balance of power in Europe had changed dramatically with the formation of Germany and Italy, the decline of the Ottoman Empire, Austria becoming a dual monarchy etc.

There were countless independence movements, France sought to reclaim Alsace-Lorraine from the Germans, Italians looked to expand their borders and the Balkans were being disputed over by the Austrians, Russians, Serbs, Ottomans, Greeks etc. You only have to read, or at least look up, invasion literature in the UK to see that there was a threat of a great war for about 40 years.

Imperialism helped distract the nations away from Europe for a long time, but once they gobbled up all they could it was back to revanchism and irredentism. So from the perspectives of people living at the time it was by no means pointless.

The alliances surely helped turned what could have been a series of smaller wars into a great war. But whether or not that's good or bad is up to debate. But after only 4 years of fighting the map of the world was redrawn, 4 Empires ceased to exist, Russia, Austria, Ottoman and German, numerous new nations were created and vast amounts of land swapped hands.

Maybe from a modern day perspective it seems unjustifiable in comparison to World War 2 because there was no Hitler, no unspeakable evil that needed to be conquered. But the people and politicians were a lot more gung-ho about war in 1914 than in 1939. Every nation and would-be nation involved, from Armenia to Poland had something to be either gained or lost.

The First World War was, more or less, the death knell of the old colonial empires and nearly ancient alliances. Long bitter disputes between the involved parties, militarization between European powers and their colonies, and blind adherence to old alliances would have led to war regardless of the cause. The assassination of Franz Ferdinand was merely one of possibly thousands of lit fuses leading to the powder keg that was Europe at the turn of the century. The beginning of the war brought countless numbers of young men to the forefront to fight for their respective nations as a celebration of war declaration. Nobody expected millions of lives to be lost over the course of a four year global conflict, nobody had seen those kinds of losses in colonial European wars, and the losses of the American civil war took place 50 years prior and was out of the common thought of the average European.

The First World War was, at the very least, a sobering event on a global stage, which is not pointless at all. The revelation of technologically advanced warfare turning colonial military strategy inside out, the possibility of losses in the millions was now possible due to new weapon technologies, and the cost of colonial hubris in military strategy was now very well apparent to the soldier and the citizen. Russia retreated from the war to ignite the communist revolution, which would lay the groundwork for the political landscape over the next century. Germany in it's humiliation and loss would retaliate two decades later under a new, unpredictable dictatorship as a direct result of the events of the First World War and the Treaty of Versailles. England and France would find their empires changing rapidly post-war, and effectively disintegrating after the events of the Second World War. The war established the United States as a contender on the world stage after breaking their policy on non-interference, only to find themselves dragged back into war again in 1944 and developing as a new global superpower alongside the USSR in the place of the old colonial powers of France, England, and Spain. The First World war effectively broke the worlds own idea of itself, turning it on it's head and casting new players into the field, new mindsets, and new horrors for the world to face.

The war, while it's causes juvenile, it's commanders incompetent, and it's methods brutal, was not pointless. After a century of history showing how the war has affected the world, it was truly the defining event of the 20th century.