I think comics and the movies are afraid to change the baseline world too much because then it'd be less relatable and require more explanation. Part of the fantasy is imagining super heros in our world. That becomes difficult if the baseline world of the comics and movies is drastically different.

That being said, I'm sure the MCU hugely sanitizes it's messages. For example, their solution to systematic racism in falcon and the winter soldier was a just a speech saying to do better.