Not likely. There are tons of webgl demos out there, performing quite advanced tasks, well beyond what this game is up to, and Firefox and Chrome produce equal results.

Example: https://zenphoton.com/

My guess is there's some sort of misplaced network hook, introducing latency into OP's event handlers, and it's producing a noticeable side-effect in Firefox, which, perhaps Chrome optimizes for, as a common, anticipated programmer tendency, that gets re-ordered behind the scenes.

Seems a big part of it was the software rendering of the filter: blur(5px) in Firefox, where other browsers are doing this in hardware. I've removed that CSS class for Firefox specifically now, and it's performing a lot better. The profiler now says 60% idle, 14% graphics, whereas previously there was no idle and it was 85% graphics.