Fish made me write better bash scripts because it gave me a proper understanding of IFS, test, and other shell “basics” since it removes a layer of automagic by simplifying the syntax. Eg fish discourages the use of `if [` and it makes you realize that the bracket isn’t a grammatical construct but rather a terribly named command.

I switched entirely for interactive use a couple of years ago and have only had positive things to say. I still use Bash for scripts but that’s exclusively scripts which I edit in a real editor with version control, 100% shellcheck, etc. and even then I’ve been rewriting most non-trivial scripts into Python for the last decade so it gets sane error handling and data structures, not to mention usually ending up being shorter due to the richer library.