In addition to what everyone else posted above regarding AI, algorithms, etc, there's a lot of people who have realized it's not a forum for actual discourse. Everything is extremist black and white to one side. Everyone posting is rage baiting at every step. Twitter has become a completely unregulated MAGA cesspool. Pressure from political entities is coloring content filtering/moderation on other platforms as well.
People need to realize the only way to make things better is to work together. Social media has generally just become an amplification of level of extremity circle jerk. Anything reasonable is "fake news" most things treated as factual are actual garbage truly fake information. There is almost no tolerance, no discussion, just ultra right leaning absolutist thinking/posting, almost entirely driven off hate and "alternate facts". I am sure similar things exist with left leaning things, but I rarely ever see anything like that on social media.
No one is right about everything, you don't have to agree with everyone else, but you need to listen and actually think. Of the group of people I went to high school with almost half of them have unfriended me on Facebook as a result of occasionally posting something that's about as central as you can get and simply suggesting we treat each other as humans, with respect and dignity, etc. THIS is driving people to stop engaging with social media.