The treatment of Keynes' post-WWI comments is an apologia that misses the deeper point. Keynes was not merely wrong about the German ability to pay, he misread the strategic situation. The French position was not merely motivated by vengeance.

The Post-WWI situation was simple in a way yet strage. Germany was defeated, yet it remained the strongest country in continental Europe. Britain and France were bled dry, Russia was in chaos and the Western Front was mostly fought on French soil. This left the question of how to settle things so that Germany does not refight the war for the same old objectives.

The French position was a Realist position - make Germany too weak to make trouble. The Keynes position was Idealist, but it needed one condition to be viable in any form: a defence alliance to prevent Germany from making trouble. Which was something that was probably politically impossible in the US, and I don't recall Keynes advocating for it.

So his contribution was to help weaken one option that was politically workable without giving a good alternative; Eventually (years later) helping to lead to an arrangement that merely goaded Germany in the wrong direction. There was a need to ask how to reintegrate Germany, but this was not served well by ignoring the strategic situation.