I confess I'm unsubbing because most of these confessions are bad or very boring.
Is that your main reason for unsubbing?
It's because I can't stand seeing some confessions as they harm my morality.
Not every sub is going to be your cup of tea, and that's fine. These are public forums, and nobody has any obligation to stay if they don't want to.  You don't need to give a reason, you can just leave quietly.
I don't care.
In this case, it is fine to not care about what others have to say.  You can leave, and the community will continue to post and engage with posts.  I hope that you can find a message board that you care about.