Why is the general consensus that the Treaty of Versailles was too punitive and harsh for Germany? The contemporaneous Treaty of Trianon and Treaty of Brest-Litovsk for Austria-Hungary and Russia respectively seem to be just as harsh if not harsher.

This is a question that has been brought up before through other, side-investigations on similar queries on AH. I have weighed in on the Treaty of Versailles being "overkill" here as well as the experience of the German delegation at the Paris Peace Conference, which should go some way to what I will put forth a well in this response. Where the linkdrop by u/hesh582 gives an excellently detailed analysis of the economic debate on Versailles' impact, I shall be focussing more on how the "Myth of Versailles" was created through the actual study of the Paris Peace Conference itself and the postwar consequences of the Treaty. Let's begin.

Before that however, I ought to address your follow-up to the linkdrop by simply noting that the Treaty of Brest-Litovsk (for Russia and Austria-Hungary) is perceived as an even harsher peace settlement between the Germans and Russians, as the government was forced to recognise the independence of Ukraine (then and even now referred to as the "bread-basket of Europe", one of Imperial Russia's most productive agricultural assets) and ceding hegemony of the Baltic regions (namely, reasserting the independence of Estonia, Latvia, and Lithuania) to Germany. Of course, as OP has already pointed out in their follow-up, the Treaty of Brest-Litovsk was abrogated (annulled; rendered invalid) during the Armistice Agreement in November 1918. During the interwar years, the political discourse caused by Brest-Litovsk was for the most part, overshadowed by the sheer amount of change which Versailles (which came later and actually came into effect) ushered in. There's a good reason why even as early as 1938 British historian John Wheeler-Bennet termed Brest-Litovsk as the "Forgotten Peace" in a publication of the same name. E.H Carr, whose status is among the most esteemed in 20th century historiography, summed this idea of "Versailles first" rather concisely in his (somewhat scathing) review of Bennet's work:

"it [the Treaty of Brest-Litovsk] was annulled when Germany collapsed eight months after its signature, and was soon forgotten in the hurly-burly of the great peace settlement [Versailles]."

With that great follow-up answered, let's get onto the main question at hand: Versailles.

Only recently, the academia on the First World War has been shifting its stance on the significance of the Treaty of Versailles to argue the stance that it was actually was a fairly reasonable peace settlement and not the terribly written piece of paper which Hitler and the Nazis repeatedly condemned and many Germans in the postwar era grew to blame for their hardships. I highly recommend that you pick up a copy of Margaret MacMillan's work Paris 1919: Six Months that Changed the World, which is a great work revising the historiographical legacy of Versailles. Zara Steiner in her book The Lights That Failed: European international history, 1919-1933 actually goes so far to point out that in comparison to other treaties such as Trianon and the Treaty of Sevres (which even more harshly dealt with the Ottoman Empire by carving large parts it up for European powers), the Treaty of Versailles was the mildest of the 1919-1920 settlements. A bold statement given the absolute dominance of "Versailles as a terrible treaty" in historiographical writings, but one which does have merit in its arguments.

A large part of the historiographical myths surrounding Versailles, and hence the dissemination of those myths into popular history teachings, stems from the notorious War Guilt Clause, which was formally named Article 231 in the Treaty. Here is what it actually reads:

"The Allied and Associated Governments affirm and Germany accepts the responsibility of Germany and her allies for causing all the loss and damage to which the Allied and Associated Governments and their nationals have been subjected as a consequence of the war imposed upon them by the aggression of Germany and her allies."

Now, many historians and postwar German politicians (the Nazis most prominently) interpreted this clause to mean that Germany alone was entirely responsible for the First World War, an accusation which they perceived as entirely false and thus nullifies the justification for any of the other punishments in the Treaty of Versailles (a reduced army, land given away, reparations etc.). The German delegation at Versailles was composed of several key figures, all of whom brought some form of political agenda and feelings towards the Treaty. At it's head was Reich Minister for External Affairs Count Ulrich von Brockdorff-Rantzau, Reich Law Minister Dr. Landsberg, Reich Post Minister Johannes Giesberts, Prussian state president Robert Leinert, financial advisor Carl Melchior, and Professor Walter Schueking. All these men had practically the same reaction to the terms when it was presented to them on May 7th, 1919: utter shock and rejection of the Allied terms. Upon receiving the Treaty from French Prime Minister Georges Clemenceau, Brockdorff-Rantzau famously remarked in his speech:

"It is expected from us that we should accept the guilt of War. This statement would be a lie in my mouth."

In fruitless protest, the German delegation sent the following note to Clemenceau:

"The German people did not will the war and would not have undertaken a war of aggression. They have always remained convinced that this war was for them a defensive war... They cannot consider the former German Government as the party which was solely or chiefly to blame for the war."

Clemenceau responded to this protest by bringing up a note from November 1918 sent by the previous German government to US Secretary of State Robert Lansing, in which Germany admitted that she was indebted to make reparations on account of "Germany's aggression by land, sea, and air."

However, it should be noted that this war guilt was not the original intention of the Article. Instead, it was the German reception of Article 231 that generated the "war blame myth". Here's historian Sally Marks on the matter:

"The question of responsibility was assigned to another commission and not addressed directly in the treaty." In Article 231, Allied concern was purely financial, and there is no mention of war guilt, unilateral or otherwise. On the principle of collective financial responsibility, the same clause, mutatis mutandis [altered but in essence the same], appeared in the Austrian and Hungarian treaties, but neither state viewed it as a war guilt clause. Germany, however, expected such a clause and so seized on Article 231, misinterpreting and mistranslating it and thereby linking reparations to "war guilt."

It was this misinterpretation and mistranslation that led to the academic consensus that the Treaty of Versailles was too punitive and harsh for the Germans, which was fuelled (especially within Germany itself) by the rise of the "stab-in-the-back" myth and the antagonising of the Treaty by the general populace. Some historians also point of John Maynard Keynes' economic works (most notably The Economic Consequences of the Peace) as influential in portraying the Treaty of Versailles as far too economically taxing on the Germans, and as a result guided their analyses of the peace settlement to highlight its 'plethora' of terrible decisions.

Sadly, modern education systems have yet to alter this portrayal of the Treaty of Versailles as overly harsh and the subsequent rise of Nazism as well as the Second World War as indirect consequences of its injustices. The modern historical academia however, has already come to that conclusion and is now shifting the consensus towards a more balanced judgement of Versailles.

Hope this response sheds some light on the matter, and feel free to ask any follow-ups on the circumstances behind the Treaty which complicated its conditions as well!

Edit: Fixed a few details regarding the Brest-Litovsk treaty and the Eastern European polities (Baltic and Ukraine).