Friendship on the rocks

We've been friends with another couple for over 40 years . Since we've all retired and because of covid we seem to have drifted apart. They live 2 hours away but we always made the effort both ways , have enjoyed holidays and weekends together etc but two things seem to have divided us over the last couple of years . Another couple started joining in with us and our foursome became six . We started to feel like the spares , then they started inviting us to stuff on dates when they knew we wouldn't be able to come , because we were away on holiday or had other engagements that we had previously mentioned .A pattern started to emerge and there would never be any discussion about changing the date of the get togethers so we could all join in .
We have a WhatsApp group which we'd previously used to arrange social events but they don't use it anymore, the arrangements are made between them and then we're invited and always on occasions when they know we can't come . We recently celebrated a big anniversary and were going to invite them to join us on a Villa holiday but 6 months before the two ladies told me they were having a girls week away and did I want to join them , on my big anniversary !! Surprised, surprise !!!
My husband now feels the friendship has run its course , he doesn't want to know anymore . We're being civil , answering messages etc but that's as far as it goes . Feeling like I'm back in the school playground to be honest and a bit hurt and disappointed that we can be so easily disposed of .Has anyone had experience of this and how did you deal with it ?