The web version clearly states that there are framerate issues.
If they make the game unplayable you could just download the windows version that to my knowledge has only minor fps issues.
As you may or may not have noticed this is a gamejam game. I do not want to spend time on optimizing (which could easily take multiple days) if it already works.
At the moment my priority is content, not optimizing for web (I don't even know if that is possible).
Also, have you tried the Level Editor? It should run well in the web version. And while you're at it try changing the occlusion mode to Keep_Lit. That should make for a smoother experience. If it's still bad switch the occlusion completely off.
I'm looking forward to your response.