RPGs are an inherently collaborative medium. Often the GM will be put in the position of the authority to shape the world and direct how it responds to players' actions, but that doesn't strictly need to be the case. In Fellowship there is a clear distinction in who can Command Lore about various things, usually giving Players the control over the lore surrounding their people (so an Elf character Commands who elves are in the setting, whether they are pixies, aliens or what have you). While this approach might not be useful in all games (such as games with established lore, like Star Wars), you can still incorporate the players' creativity in how the world works on a smaller level.
In our lengthy Princes of the Universe Exalted campaign we ran into an interesting situation. My character wanted to unite the setting's dysfunctional bureaucratic heaven to work for our characters. To that end, I suggested the character would go on a quest to find an artefact, the Crown of Thunders, and use it as a symbol to rally the bickering gods. The Crown had an important symbolic meaning to the gods and the Exalts, but it wasn't a concrete "this crown makes you a ruler of the heaven and solves your issue" thing. As such, some other players dismissed the idea, but the GM rolled with it without hesitation, and even the various NPCs started reinforcing the idea soon after. It was a nice way of approaching problem solving in RPGs - a player's idea becomes a solution to the problem by the dint of player suggesting it as a solution.
and establishing the Creation Ruling Mandate
As Fellowship hints, the GM is there to create problems for the players to solve. If they were to create solutions, you would either run into GM-PCs that have the foresight given to them by reading the script, or else they might be forcing the players to figure out their moon logic to solve a problem the way they envisioned. Either solution wouldn't be good. Since you can't expect the players to come up with the same ideas as the GM, then of course you need to allow for some leeway in how things can be solved, how the world will react and so on.
You should be leaning into those ideas as a GM - not only asking your players what they want to do, but also what they want to accomplish with their actions. There is a difference between "I want to beat the guard up" and "I want to beat the guard up to rally the common people to storm the bastille with me" - one sounds like the combat is the end-point, while in the others the violence is a means to an end that might not be clear if it's not spelled out explicitly.
By talking about the desired outcomes you can set the correct expectations and let the players know if their actions won't have the desired outcome. It's best to be up-front about such things than to let players go goblin brain down a dead end. Sometimes that can be a "no", sometimes that can be a compromise ("if you beat this guard, that will work in your favour for convincing the people to rise up"), and sometimes it can lead to some different ideas being worked out ("maybe if you rally the people first and come in as a mob, the guards will actually join your just cause?").
Conclusions
Try to incorporate your player ideas into the game - you are here to create the story together, and it's good when the world conforms narratively to the player actions and ideas (whether that's reinforcing it, or fighting back against it in a satisfying way ("hey, would you want the system to try crushing you and throwing you in jail for daring to fight the guard to show how the government will oppress you, making your character a martyr?")). Just saying something "won't work" without offering some alternatives isn't as fun as championing even some wacky ideas.