Colonialism didn’t end after WW I. On the contrary, it reached it’s zenith during the inter-war period. European countries began to let go of their colonies after WW II, mostly in the 1960s, and of course the USA let go of the Philippines in 1946.

“The world didn’t make much real progress, in fact, until the 1990s or so…”

I’m not so sure what was so fabulous about the 1990s. There was even war and genocide in Europe in the former Yugoslavia. Other Europeans just sat there and watched it happen. There was the Rwanda Genocide, and the first and second Congo Wars killed something like five million people. There was the invasion of Kuwait and the First Gulf War. Afghanistan, Sudan, Sri Lanka, Sierra Leone, Burundi, Liberia,and most of the former Soviet Republics had civil wars. There were the brutal Chechen Wars in Russia. People have short memories I guess.