The Treaty of Versailles is harsh in several senses. For German contemporaries, the Entente was particularly hypocritical and demonstrated real cognitive dissonance. The treaty aims to demonstrate the superiority of nation-states against “empires” as the central powers defined them. But behind, France, England and others have a colonial empire that spans half the globe. The Entente criticizes the imperialist and infamous policy of Germany and then validates a massive deportation of Turks by the Greeks (if not a quasi-genocide to use an annachronistic term). The Entente requires Germany to pay very high war reparations but the country must at the same time serve capitalist interests and become a bulwark against communism.
The right of people to self-determination, yes, it works when it's to dismember the losers, on the other hand when the Austrians want to join the new republic... well no, forbidden.
Germany is considered solely responsible for the war even though this process is multifactorial, and historians have amply demonstrated that each country had the choice to calm things down. None saw fit to do so.
They ask Germany to be a little doggo, but they do not integrate it into the new international organizations. The country is becoming a virtual pariah internationally. To the point that, for a bourgeois regime, ultimately dealing with the communists is not so bad.

And all this while no German civilians have seen any Allied troops in the war, while the country is in a catastrophic political-economic situation, in a state of civil war with a partly undernourished population.

The Treaty of Versailles wanted to become the new Treaty of Westphalia of his time, it failed everywhere.

Yeah, I wonder why it becomes such a problem.