I think there's a natural drifting away, if you like, when friends have kids and you don't.
Not every time, but I see a lot of posts on MN from mums who claim that they've lost their friends after having kids and blaming their friends/kids for it-and not looking at their own behaviour. What I mean is-some of these posters will freely admit that they regularly cancelled on their friends, didn't speak for months at a time, and basically put forth no effort in their friendships but fully expected their friends to remain there for them when they wanted them.
In some ways, it can be understandable why this happens-being a parent, especially a mum, is tough, and if you have no support network and the kid is young, even tougher. So it makes sense why, in those instances, a mum may struggle to maintain friendships or be able to attend anything that she can't freely bring her child to.
So, for those friendships, if they're not totally a lost cause and are a good friend, I'd probably accept meeting on their terms for a bit. Have them as the friend that you go for coffee with or to the park for a walk with-etc.
Of course, it could be as I described and no effort is forthcoming from said friend/s, then I'd just distance myself and focus on making friends with fellow child-free people.
A lot of the advice given to the posters I described on MN is that they can return to those friendships once a few years have passed and the drudgery of parenthood has gone. The reality is, that's just not the case. Many people won't be willing to return to friendships after being left in the dust, even if they understand the reasons.
Things change. I accepted long ago that choosing to be CF would always be an anomaly and thus, I would have to adapt to the changing friendships and accept that there would be friends I'd lose. It's just how it is.