My kid has been in a gym where - and it truly sucked - I was blown off. Nothing ever changed unless it got worse. If I had concerns, everything was always dismissed or twisted to be the kid's fault or my fault. I was not spoken to as an intelligent human being with a possible legitimate concern. If my HUSBAND was there, it was a different story. Still, nothing would change, but the tone of the conversation and defensiveness to everything I said was better. I didn't want my husband to have to be there. He didn't want to have to be there. But the fact was that concerns were treated differently when he was present. The owner is an old-school misogynist. The coaches were more reasonable, but I could not work with the owner at all. We could have gone the confrontation route. My husband could have gone to talk to him about the issues as they progressed. That might have allowed things to go on a little longer, but who wants that? It's just a band-aid. If you are in that kind of gym, I'd suggest looking elsewhere. They don't change.
OP, you know the answer here. Nothing has changed in the past, it won't change in the future. And time is slipping by. His coach has clearly cut him off. We've been there, done that. We tried. We tried to be patient. We tried talking to the coach and gym manager. We tried encouraging our kid to do the best possible with each day. We just delayed the inevitable and made it harder for her to bounce back when she did change gyms. If your son isn't getting attention, he's falling behind. It's hard to catch back up. This isn't just impacting his scoring potential, it's impacting his mental and emotional game. It's impacting his ability to build on the foundation he does have. Go now. His happiness, mental toughness, and development are more important.