I think that at this point in my life, I can tell the difference between an abusive person vs a good person with some mildly toxic behavorial patterns. Of course, I do always see people posting about incredibly abusive assholes that they really need to break up with, but in my opinion there's a lot of black and white thinking in places like relationship_advice. People who are maybe something like 20% jerk get lumped in with people who are 80% jerk.

A lot of people just don't have a spine and need to stop putting up with bullshit, on the other hand human nature is flawed, and it's unrealistic to expect people to act like angels all the time.

edit: To clarify, I'm looking for a subreddit that teaches you how to work on an issue, rather than give recommendations on whether they think OP should cut this person out of their life.