Thank! During the jam, some people mention it about using a mouse look kind of camera. It wasn't part of my original idea. The game was intended to be a kind of 2.5d platformer at first, then evolved into this "open world" style, that's why I never bother to "fix" the camera with the mouse.
I've started to work on an update right after the Jam, in feb/march 2021. But I had to abandon the project for personal reasons.
Then another jam came in, and I never had time to fix or improve this one.
Maybe after I complete my actual project I'll return to this one, and probably would use your suggestion.