I used to have Vim with dozens of plugins installed, nowadays I consciously use Vim without relying on any plugin and try learning to do the same with only the basic movement commands, so I can be productive no matter what machine I'm using/logged into today - otherwise they'll be forgotten (hackers used to survive in the original vi without visual mode or multiple undo, I think surviving a pluginless Vim shouldn't be difficult). Some for the shell.
This hasn't happened to me. I guess I've never used my prompt as a programming environment, so switching from zsh to fish hasn't impacted by ability to write posix shell script anymore than it as impacted my ability to write ruby or javascript.
I use fish strictly as a command line and it is fantastic.
bash is installed by default on pretty much everything but for fish I need to un-learn bash shenanigans like `esac` which I fear would hurt more than help in general.
Either that, or maybe I'm just lazy and missing out on a nice tool...
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.
If you mean that you still have to use bash on other machines: yeah, I feel you there.
At least for me, I'm fortunate that if I end up using a machine frequently, I can just install fish and add my config/dot files.