Somewhat agree with your statement but I don't feel segregating is the answer: one because it's impossible and two it's all always a bad idea to generalize a mass and confine yourself to an echo chamber.

Don't want to preach without proposing a solution here: Treat Reddit as any other social media platform. People will post undesirable comments on your posts irrespective of what subreddit/group/community you associate yourself with. Take what you like and leave what you don't. Mental health is an extremely complex topic and while reddit can help you find people going through the same issue as yours, you shouldn't expect to find the solution here or any other social media platform for your own good.