This is a cute idea, and I'm always a sucker for the "3d environment with 2d sprites in it" type of visual style. I like the concept, and it could be fun if combined with some basic first-person platforming (which is sort of already in the jam build, with the character on the roof and all.)
The performance problem with your web export might've been due to shader issues or something? Godot 4 is still pretty temperamental about these, unfortunately. But the desktop build does run so that's fine.
Best of luck in the future!