Often in our society we get the word “naive” passed around. I really dislike that word. It only exists as a means of deriding whose who are courageous or optimistic.
It’s only ever a cultural stamp against, usually, those who dare shake things up and challenge the status quo with their own ideas, or those who have faith in themselves and are confident they make the world better for even themselves.
On top of that, it’s a very condescending word.
If you want to refer to foolishness, I suggest you simply use the term foolish, or hopeless, to refer to hopeless and foolish ideas, or stupid. But do not go around randomly using that to stamp down the optimistic and the courageous just for its own sake.