Jumping in here because I had the performance issue too, and pretty severely. In my case I was getting around 2 FPS, and I tried the game in two different browsers, on three different days, and across three different networks, so I was able to rule out quite a few variables.
I didn’t realize there were quality settings though, so that’s one thing I didn’t test. Do you know what quality level the web build defaults to?
Seeing a few other people mention the town specifically also makes me wonder if there’s something happening there beyond just overall graphics quality. If you keep developing this after the jam, that might be an interesting area to profile.