Why?
Another perspective…
Presumably every one of those other mums at the playgroup will also have had a first time experience too. Why did they stay and keep returning week after week if it’s such a horrible group?
Also, they’ve probably paid a nominal fee to attend a baby group with their babies and probably look forward to grabbing an hour for a coffee and a natter with ‘Jane’ and ‘Trish’ whilst their children play. Perhaps they’re painfully shy too and don’t have the confidence to talk to a complete stranger.
The only people at fault here are the people meant to be running the group. They’re the ones who need to put plans into place to welcome new people. However, with most volunteer led groups, the group dynamic depends on the social skills of the individual volunteers and obviously this varies enormously. You’ll probably find that the people running the play groups are the ones who end up involved in the PTA and Brownies etc.
I used to run a baby & toddler group when I had my toddler DS. I organised weekly rotas so that members had a job such as welcoming new members, making drinks, organising snacks for the children, setting up and tidying away etc. It ensured that everyone contributed something and it wasn’t left to the same two people every week and allowed me to spend a bit of time playing with my DS too. However, for some people this was too formal and they just wanted a space to come and chat where they didn’t have to actively do anything.
When you go clothes shopping, you don’t try on one item and then leave declaring all shops are useless as they only sell the wrong size or style? There’s no right or wrong way but surely you’d try several groups rather than dismissing them all out of hand as ‘cliquey’ and blaming complete strangers for not meeting your specific needs?