"Have fandoms become more toxic in recent years? What is going on?"
I pretty much agree with what was said here. My problem with Twitter and Facebook (I don't use Instagram or any of the other social media things) is the fact that, while it is very easy to block/mute individual users, there are just so very many shitty assholes on those sites. If you dedicated yourself to blocking shit-sludge on Twitter, you could be there until the heat death of the universe and still not have blocked more than a small percentage of them. That is why I have almost entirely abandoned Twitter (outside of Seth Abramson threads) and have Facebook highly curated. But even then, with Facebook, on otherwise innocuous stuff like the Star Trek and Star Wars FB pages, you still have to deal with myriad toxic shitheads down in the comments, assuming you, like me, are dumb enough to keep trying to read comments on such pages. And heaven forbid you dare to look at comments under a post by, say, Hillary Clinton or Barack Obama. The toxic deluge from asinine dumbshits under those is enough to poison a continent. I've blocked literally thousands of dumbfucks on both Twitter and Facebook, but it does no good. More just keep crawling out of the woodwork (or the ones you previously blocked just keep coming back with new accounts).