It’s okay - DMing multiple campaigns for sweaty tryhards just massively overprepared me for anything BG3 could throw at me 😅 the solution to many dumb character builds is talking to them about it outside of the game like an adult “okay, roll me a [weakest stat] save”.
Many bosses will be immune to several effects, and scouting what exactly you’ll be facing is time consuming if even possible, so it definitely can fall into a “run into fight - oh I need change my spell list - reload quicksave” which is a little lame but you can’t always be prepared for everything unfortunately.