I'm guilty of the "ditching friends after kids" thing. I gotta say, it's a major bummer on my side as well because friends are few and far between. Having kids makes life very different though. Leaving the house used to involve me throwing on my shoes and slicking back my hair. Now, we have a baby bag that inevitably needs something packed (change of clothes, snacks, diapers, wipes, blankets, pacifier), 2 babies that need their diaper changed right before we head out the door, have to make sure they are fed, dressed, and cleaned before leaving, and then we get to deal with the baby who threw up as we are halfway out the door while the other one is screaming. Don't even ask me to hang out without mama and the kids lol, I'm sorry but leaving the kids with her while I go to work is tough enough.
Maybe see if you can visit them, a game night or movie night? Ours are babies, so we do movies and pizza when my bro or friends come over. They love it, and it's low stress all the way around.