In a single one-off program or something that's already fast enough to not take more than a few seconds—yeah, the time is spent better elsewhere.

I did mention for a compiler, specifically, though. They're CPU bottlenecked with a huge number of people or CI build agents waiting for it to run, which makes it a good candidate for squeezing extra performance out in places where it doesn't impact maintainability. 0.02% here, 0.15% there, etc etc, and even a 1% total improvement is still a couple extra seconds of not sitting around and waiting per Jenkins build.

Also keep in mind that adding features or making large changes to a compiler is likely bottlenecked by bureaucracy and committee, so there's not much else to do.

There was a series of books in the '80s where a systems programmer gets pulled through a portal into your typical magical world, good vs evil, etc.

They subsequently look at the magical spells in use and realise they can apply Good Systems Programming Practices™ to them. And thus, with their knowledge of subroutines and parallel processing, they amplify their tiny innate magical abilities up to become a Pretty Good Magician™. So while all the rest of the magicians basically have to construct their spells to execute in a linear fashion, they're making magical subroutines and utility functions and spawning recursive spells without halting checks and generally causing havoc.

It's quite a good allegory for modern times, where a select few build all the magic and the rest just have useful artefacts they use on a day to day basis with no idea how they work