I'd argue that the or at least one major reason for the downfall of Stackoverflow (and not just a catalyst) has been a surge of Indian IT people triggering an avalanche of extremely low quality questions and answers. I've been a big fan of SO since about 2010. Not just didn't mind the harsh moderation but actually attribute to it learning how to properly ask a question. But at some point round about 2019/2020 it stopped being fun due to it going from knowledge base to garbage dump.

Related, every time you see on SO "please mark this answer as correct" it's usually not correct