I know it's fun to scoff at "those front end guys" and act like you know all the answers, but if you do know the "one true solution" to this please tell us.
It's "unsolved" in the sense that all the current solutions feel wrong (but work great), and if that's the biggest problem front-end development currently has, then it's in a pretty damn good place.
I really don't know the answer. I'm a front end guy too.
But it just seems like we are all stuck on this collective transe of needlessly complicated, overly fashionable tools that struggle with the basics.
From what I've seen (granted, not much), animation and styling look like an after thought, which is surprising.
But I'm weird, I still write bare CSS to this day whenever the decision is up to me.
SASS is cool, but not enough to justify adding another lever to the machine, IMO.
It's "unsolved" in the sense that all the current solutions feel wrong (but work great), and if that's the biggest problem front-end development currently has, then it's in a pretty damn good place.