[MicroBob]

Telling somebody directly "Hey, I've decided I no longer want to hang out with you" would be pretty damn hurtful.

Just drop-out and/or stop accepting their invitations to stuff.
Go do stuff on your own. Make up excuses. Whatever.

This isn't complicated. You had a friend or three who you don't feel that keen about now. So you just stop hanging out with them. No need to tell them that there's a reason you think they suck, etc etc and no need to try to bruise someone's feelings like that.

And a year or two later or maybe longer you might have a good time reuniting/going out with them again sometime and remembering all your fun times together.
No need to burn bridges either.