This depends highly on the domain. I'm the only person on my team with any level of frontend work in the past ~2 years. And when I did, I was able to consult with UX experts and designers.
I can't say that theory is more universal than frontend, though anecdotally, for me, it is. But ui isn't universal.
I can't say that theory is more universal than frontend, though anecdotally, for me, it is. But ui isn't universal.