On the Mac, Firefox is Firefox, with Quantum and all. It's iOS where Firefox, like every other third party browser, is mostly just reskinned Safari, because third party browser engines aren't allowed due to apps being restricted from running outside code.
I use Firefox. It works OK. Is that why I think the Google docs are not very good?
I am on a Mac (for work) so in reality I am using Safari it seems from what I have been reading!