Chrome and Firefox and Opera all keep up. Safari is worse than IE/Edge at this point in terms of implementing standards. It's the absolute worst because it's not even available for anything but Apple products now so it's a pain in the ass to test.

IE is dead. Edge is embryonic. I can't speak for Opera. I use Firefox every day, both as my personal browser and as my primary development target, with validation in other browsers performed via automated and manual testing. And, if Chrome is your standard, Firefox cannot honestly be said to "keep up". It's consistently a few versions behind, at least, in supporting major innovations which reliably appear first in Chrome.

I grant testing is an issue if you don't own Apple hardware, although there are free and inexpensive remote testing services which cover that need well, and I'm certainly not about to say that Safari doesn't pose any unique difficulties to the web developer. But so does every other browser.

I'm a firefox user as well, and it's both my personal browser and development target. Safari is the only browser that consistently gives me issues.