There's definitely a balance to be struck, and it depends on the table. I would only do this on a table where the rules are actually just guidelines.

For many others, a world needs to make sense internally. It doesn't need to make real-world sense, but within the world with its different reality, things kinda need to be consistent. For example, if it is easily possible for a wizard to circumvent your will save by asking a trick question, the whole world would look completely different. Almost everyone who interacts with any kind of wizard would be extremely guarded around giving consent for anything since it might just be a ploy to remove their resistances.

A resourceful/logical player would now try to trick an NPC into agreeing first, and well, if it doesn't work, you can still cast the spell normally, nothing lost. You could ask them to stop, or they could recognize themselves that doing it like that wouldn't be fun, but if you act in the world you usually always try to make the best decisions. If you artificially limit that in a fourth-wall-breaking way, the game actually starts to lose its appeal.

If you allow stuff like this all the time, eventually the alternate reality of your characters will just become a random clown show. Problem solving will just be about who comes up with the most ridiculous thing that makes everyone laugh about its absurdity. There will be no logic or rational thought involved anymore, it'll be no simulation anymore, just a sandbox. Which again, might be fine for certain tables, but many want to be able to immerse themselves in a different world that they can accept as at least possible, which is the actual fun for them.

So no, you aren't necessarily "not fun" if you don't allow this as a DM. You're just playing a different kind of game with a different kind of fun.