Keep using Chrome on your mac, then (though be aware that there are 0-day exploits found for Chrome on a somewhat regular basis too), or even better: Use Safari. At least it's not Chrome. Fight the monoculture.

The vast majority of computer users are still not using MacOS and those people can also do some good by using Firefox even if you can't.

When it comes to "slow" and "resource hungry" the Firefox devteam is very responsive to bugs. I've had approaching a dozen performance issues I personally reported get fixed.