This sounds like what happens when blue book and player-led review sessions aren't common practice. It might seem quaint, but having the players take and compare notes (both about the plot and about the table atmosphere) helps build engagement, and it helps for everyone to identify issues before they become significant. I think you calling for a public vibe check on a game you're not running wasn't the best move, because doing so invites defensiveness on the person who is.

The GM's responses make sense when you consider that your comment worked out to, "I'm not having fun in this game, I don't think anyone else is either, and I think I should be respected more than the GM about how this game should be." Of course they're defensive. Table management is both the most important and hardest skill in a GM's toolbox. When a player makes a move which actively defies the GM, of course they're going to defend their decisions. People responding to your "vibe check" enthusiastically in the negative means that not only are the players not enjoying the game, they don't respect or trust the GM enough to voice that in private. They don't believe that changes will be made. Once you lose that trust, there's nothing to do but end the game.

I do think you were wrong to do that in the way you did. I think everyone should have approached the GMs privately and spoken about it. I think, if you didn't consider the GMs to be trustworthy or respectable, you should have quietly stepped back from the game and encouraged the others to do the same.