This tells me that the players are passive in their role in this game. The DM presents something and the player can provide a thumbs up or down, but no significant input. Even if the players all did fundamentally vote against the DMs idea, the DM is under no obligation to abide by it since the game is not for the players but him. It's HIS art, they are there to consume it.
That's not exactly what I meant, and I think my description is colored by all the board game design I've been doing lately. The whole point of that kind of art is to package a specific kind of striving experience into a box and hand it to people who might be interested in having it. A playtester finding a snag or a weak point or feeling dissatisfied or disengaged with some part of the game is useful feedback, and useful for testing what a design is doing, but (at least in my process, I'm sure there's more discovery driven designers) doesn't generally lead to changing the goal you're trying to deliver. You get a lot of suggestions that you politely ignore because they have nothing to do with the experience you're trying to produce or are counterproductive to the end you're after.
In TTRPGs, generally, I pitch a premise, a setting conceit or maybe even a system, see if anyone is interested and if so, go develop it into something playable. I've done a lot of that a few times already. I have mythic roman empire in decline setting ready to go, I've still got notes and development on my one massive country losing its divine central figure and falling into civil war game, I have a fantasy pastiche of Firefly lined up somewhere, etc. etc. If I run something new again soon, I'll rifle through those, see if anyone likes one of them and either get back to developing it or do something new.
When I say "directionally" I mean there's no point in developing a setting my players aren't interested in playing. If they all want to be tortles, then I will make sure I've put together a setting that accommodates tortles. What I'm saying about "co-designers" though, is that the portion of "play" that drew me to DMing in the first place is sitting down to create an interesting setting, full of problems and competing forces that lives up to the implications of the systems theoretically making it all tick. It is a thing that would be fun to do without players at all. Having them is a constraint that guides what I'll make, much like, say a board game publisher looking for a trick-taking game about a specific period of art history.
That goes beyond if I can play a Tortle or not. That is a fundamental issue with the power dynamic so brazen it borders on offensive. I don't know if it was intended, but it reads like the players are there to glaze the DMs creation rather than the DM presenting something for the benefit of all the players.
If they don't like it, we're not going to get to keep playing, so I'm incentivized to make stuff my players enjoy. I'm not writing a static travelogue, and frankly I prefer very clear and powerful rules for player interaction precisely so I can see what happens to the stuff I've built. It's more analogous to something like architecture, where you can't actually control how the city develops, you just lay a plan and try to produce a specific experience.
So if tomorrow, you propose something and EVERY player decided they didn't want to play it (or even the majority didn't) are the players in the wrong for forcing their preferences on the DM?
I'll give a more concrete example. DM is wrapping up a campaign and says "I want to do so different. Next game I'm running Star Wars EotE". And four players say "I'd rather not." (One doesn't want to learn a new system, one prefers fantasy to sci-fi, one specifically hates Star Wars, etc). And they would prefer another D&D game of any stripe. What should we be doing to remedy this? Because the bulk opinion I'm getting is "kick the four to the curb and find new people who support your vision." And I feel that's such an extreme position that it only works in hypothetical Internet discussions when people are trying to be hardcore. Is Star Wars worth 2/3rd of your current players? Do you change your preferences for the sake of the group or give them the ultimatum of my way or highway?
I'm either going to propose a different game then, or ask someone else to run something. I've got maybe 7 or 8 people I could reasonably game with before I'd need to go meet anyone new, and I don't really play with more than 4 or 5 of them at a time. There's several different games/groups going all the time, I play in some of them and don't in others outside of what I'm running. If the thing I want to do appeals to some other combination of them, then I'd play with that group.
Really, this has never been a problem. The biggest constraint has always been scheduling.