I worked mostly on frontend in 2012-16, in plain HTML+CSS, and then quit, because React was required everywhere, and I tried and hated it.

But before React, I don't recall frontend as very inspiring and joyful.

It was fun to see your work immediately on the screen. I did apply skills and had to solve some weird situations. I could optimize our CSS with OOCSS approach (later used in Bootstrap) -- only to complaints -- semantics! too many classes! (my trump card was that their commits contained +200 lines of CSS, while mine mostly had 0 -- and our CSS was already bloated into several megabytes).

But this was a dead end. I tried making tools to find out unused styles, to automate some patterns -- like click a button and load some content over Ajax. But the guys, who copy-pasted code with dumb solution to this, got 2-3x more tickets closed. I proposed a tool to make screenshots of pages and diff them to search for regressions, but the response was it's heavy RnD, we're not a research institute, we got to ship the next popup tomorrow, etc.

Nobody gave a shit much earlier.