Kobold Boots, I'm not sure I understand, because I think you described most of my gaming group, but implied it was a bad thing.
My gaming group is a loose conglomeration of folks who game together and who all met through gaming one way or another. Over half of the folks in the group want to GM occasionally, in whatever system or campaign strikes their fancy. We usually have two or three campaigns that various members of the group are active in, and those campaigns have flipped all over the place during the years.
When someone wants to start a campaign, they get to pitch it to whomever they think would be interested and would be the best fit for the game they want to run. "Fit" is determined solely by the GM of the campaign being pitched. It could be scheduling, it could be gaming preference ("Bob only likes action campaigns, this one is going to be low combat and high politics"), proposed time commitment ("I won't invite Alan, since I want a weekly game and he can't do more than biweekly."), or even just "I want a four-player game, so I can't invite everyone". It's not a judgement of the people involved, just of what you think is right for this particular game.
If someone spins up a game and you weren't invited, all that means is that you weren't invited for this game. We're all still friends, we're in OTHER games together. I might not know why I wasn't invited to whatever new campaign, but I don't worry about it much. In fact, sometimes folks mix up the group and intentionally exclude some folks because they want to see how a game would work with a different mix of people. (We have more people in our extended group than would work in most single campaigns.)
We don't try to ignore people's feelings. If I know that Alice is just DYING to play in a cyberpunk campaign, I'm not going to exclude her if I run one. But if I'm pitching a Wizard Academy campaign and I think other folks would work out better for it, I'll work with them and leave the rest of the group outside of it. I don't feel there's any reason that anyone needs to know every single game we're all playing in. It's not a matter of keeping things secret, but rather, why should they be consulted on everything that we do, if it doesn't involve them? I wouldn't consult the gaming group if I decided to join a softball league with games that didn't conflict with the campaign, after all.
For us, this has worked out well. We've run short term games, longer term campaigns, one-shots, etc, and we're all still friends. I think the fact that we have so many people excited to GM and run new games is a GOOD thing, not a problem we need to address.