The question it, what is your aim?
Are you trying to earn as much profit as possible? Or to create something because you enjoy it? Or something in between?
I’ve made games in the past that thought they would flop, but released them anyway, and they were better than expected. I’ve also made games I thought everyone would go crazy over, but at the end nobody cared about. I don’t think a prototype is enough to tell if you should ditch it or not, especially if that’s based only on your decision and not random people’s feedback.
Personally, I develop games for fun, so if I’m working on a project that suddenly I stop enjoying, I either change the game to make it more fun to work for, or wrap everything up and publish it as-is to start a new one (if it has enough content).