I've tried Twitter a few times and I always leave this exact reason. I wish there was some more filtering or tagging options... so I could subscribe to @someone#research or @other#hobbies, and avoid all the noise. Some people have dedicated accounts, but it seemed to be a minority, I wish it was more common.

This is an issue with social media IMO. Not everyone uses every platform, so people without Twitter post politics/memes to Instagram (which I find really jarring) and those without Instagram post personal photos to Twitter when followers might be expecting just opinion/knowledge. Presumably platform owners have decided that channels per account are off putting for most users.

This. Having sub-channels in social media is long overdue. It will be a killer feature. If I want to post baby photos I can freely spam the "family" subchannel who will be more than happy to consume it. Similarly we can cater to a different set of followers with tech posts

I just unfollow anyone who does that. There are quite a lot of people who just stay “on topic”, more than enough to fill a feed. So while I might miss some interesting content from people I otherwise unfollow, it turns out a lot of the time someone else retweets it anyway.

Unfollowing itself when you see something off topic takes very little time.

I do agree with the other reply that being able to subscribe to topics from people would be awesome, but in the meantime it’s pretty good if you maintain a zero tolerance policy for off topic stuff.