But while you are at your job anyway, might as well make it slightly less of a drudgery while you are at it.
(Eg I quite like functional programming. Both because I like the style of thinking, but also because I don't trust myself nor anyone else with code; and eg a heavy emphasis on immutability means that I'm less likely to get woken up in the middle of the night with some production problem.)
Taking a mercenary attitude towards work works just fine for me, and keeps me overall happier.
Per your example, I like FP and immutability for the same reasons (won't get paged as much), and I'm always reading to stay up on my game, but it's still just work. If you worked with me, you'd probably think I live and breath this stuff as a passion because I put so much time in to stay so much on top of the tools available. But I hate programming. Hell, you might even say my hate of it drives mastery in the same way your passion drives your mastery. To me, it's just a tool by which to automate things I do care about (and retire younger than I could in other roles).
About FP and immutability specifically:
You don't have to go full on and re-write everything in Haskell. Small scale decisions can already make your life easier without much disruption. Eg if you are using Python, by default stick your information in frozen dataclasses, and only deviate from that with good reason.
Another thing I have a minor passion for is to as much as possible handle corner cases in the main line of the code.
Eg instead of having a big 'if' at the start of your function to handle an empty list and return early, try to make sure that the main logic can deal with empty lists just fine.
After all, the simpler your control flow, the easier it is to get code coverage in tests and production.
(I mention `and production', because in practice, lots of code is battle-hardened instead of sufficiently tested.)
This is why I keep my mouth shut IRL about just wanting the paycheck. I'd imagine a lot more than a tiny minority of people are just there for the job where you've worked. We just keep our mouths shut because the passionate folks judge us paycheckers.