I've found that I too have stopped hanging out with a lot of old friends, mainly because our friendships were based on circumstance / proximity or shared hardship more than shared values / thought processes / beliefs.

Most of my strongest friendships have tended to happen with people who share some of the same core values that I do but who are fundamentally different than me in other ways. This makes the relationship very rewarding as every conversation is a potential learning or growth opportunity for both parties.