There’s also the problem of what is installed universally, and having to know both bash and fish.
If all you ever have to deal with is a single CLI on a single instance, and you never ever have to deal with any other system in CLI mode, then I’m sure that switching to a more modern shell can be useful and a good thing.
Until you do have to deal with a different system that has a different shell installed by default.
Give me a shell that is literally 10x better than bash, and is also installed universally, and I’ll make the switch. Until then.....