As far as I know, the reparation payments were delayed again and again, and only a tiny fraction was ever paid before the treaty was scrapped, so Germany's major economic troubles can't have been caused by that.
Also, it seems to me that the real problem with the way WW1 was concluded was the lack of an occupying force in Germany that could actually enforce the terms.
What I'm mainly wondering about is this: how did the theory of the Treaty putting Germany on the path to a new and almost justified (from the way many speak of it) war of aggression come to be, and why does it seem to be widespread today?
Well, the Treaty was humiliating and economically painful. That much is very, very evident. The fact that Germany had so much trouble with the reparations only serves that point.
This thread has more information on how punitive it was.
Some highlights of why people typically attribute it to the rise of Nazism as well:
- Germany would be prohibited from peacefully uniting with Austria (this later served as propagandistic justification for the Austrian Anschluss by Hitler)
- Strict limitations on the German military were imposed with respect to its size, budget and organization (this later weakened the Weimar government so much that roving bands of politically motivated militias, the Spartacus Bands and Freikorps, would be able to openly fight in the streets without needing to fear government authority; later, Hitler's Brown Shirts would enjoy the same freedom of action)
Typically, there's also the issue of people and their abilities to jump to conclusions. I won't pretend to know whether or not the treaty really did spawn Nazism, or merely created a vacuum it could fill, or had no effect at all; personally, I think it's the middle, but someone more educated on it can give information there.
However, the idea is perpetuated constantly, as you point out. Why?
Well, few reasons:
People don't get the complexities of history very easily or quickly. /u/NMW did a wonderful write-up on second-option bias, which contributes heavily from what I can tell. People on this subject tend to be stuck in Historiographic phase I, where they hear in school that Hitler did this and said that the German people needed to "regain their honor" or some variation of that.
Hitler himself did use the Treaty as justification for his actions. He made a speech in 1923 on the subject, talking about how humiliating the treaty was:
So long as this Treaty stands there can be no resurrection of the German people; no social reform of any kind is possible! The Treaty was made in order to bring 20 million Germans to their deaths and to ruin the German nation. But those who made the Treaty cannot set it aside. As its foundation our Movement formulated three demands:
- Setting aside of the Peace Treaty.
- Unification of all Germans.
- Land and soil [Grund und Boden] to feed our nation.
Our movement could formulate these demands, since it was not our Movement which caused the War, it has not made the Republic, it did not sign the Peace Treaty.
This was just a few months before his failed Beer Hall Putsch, by the way.
Third: I hereby declare that the section of the Versailles Treaty which deprived our nation of the rights that it shared on an equal footing with other nations and degraded it to the level of an inferior people found its natural liquidation in virtue of the restoration of equality of status.
Fourth: Above all, I solemnly withdraw the German signature from that declaration which was extracted under duress from a weak government, acting against its better judgment. [sic], namely the declaration that Germany was responsible for the war.
Now, I can't be sure that Hitler really thought these things, or whether he was simply using it to his advantage. However, it's not unreasonable as a result to see that the Treaty was used as justification, and appears to have had a very big impact on the German nation.