As a fellow fish user, I agree. Occasionally I write fish scripts/functions, but they're for my environment so I don't expect them to run on other people's fish shells, let alone bash. Then when I am in another shell, I can usually get by on the minimum (glob, pipes, redirection), which is mostly fairly universal. And when I'm not SSHd into some other machine (which is 99% of the time), then I get all the superpowers of fish to use.
It's a bit like the equivalent vim argument. Yes, using unmodified vim means you have access to the same tools in every environment. But I spend 99% of my time in one environment, so I'd like to optimise for that one, whether that's by using an IDE or installing a bunch of vim plugins and customising everything. Then when I do need to SSH into a server somewhere, I can get by on the bare minimum - in my case, usually nano. If I'm using nano for long enough that I start missing my IDEA features, then I've been using nano for too long and need to figure out a different way of deploying/debugging changes in the first place.
It's a bit like the equivalent vim argument. Yes, using unmodified vim means you have access to the same tools in every environment. But I spend 99% of my time in one environment, so I'd like to optimise for that one, whether that's by using an IDE or installing a bunch of vim plugins and customising everything. Then when I do need to SSH into a server somewhere, I can get by on the bare minimum - in my case, usually nano. If I'm using nano for long enough that I start missing my IDEA features, then I've been using nano for too long and need to figure out a different way of deploying/debugging changes in the first place.