You like what you like, but I just want to point out that as a Firefox-first user, when I switch to Chrome to check that whatever I'm working on is cross-browse

You like what you like, but I just want to point out that as a Firefox-first user, when I switch to Chrome to check that whatever I'm working on is cross-browser functional, I am struck with how bad Chrome looks. So I think some of what you perceive as "modern" is just what you're used to, and a short time after switching it will not bother you. But, of course, you like whatever you like.