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.
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.
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.