I tried fish and really liked it until I tried to run one of my numerous helper scripts and was faced with syntax error; too lazy to update so many scripts.
Did you try "bash <script>" or adding a #! line, which scripts should generally have anyway?
Not the op, but that only worked half of the time when running install scripts from the internet. To make it really work you basically had to setup and maintain a full bash environment in parallel to the fish environment (env variables, paths, etc...). Most software packages out there really expect that you're running in a bash-compatible environment.
I launch a bash shell, which inherits parent fish shell's env, then run the command and exit back to fish.
All my scripts have "#!/usr/bin/env bash" at the top but in some cases that didn't help. Also, I think some bash specific bits in my .bashrc had syntax errors. Eventually I just didn't want to deal with the hassle of switching over.
Same for me, later I switched back to zsh after I discovered this plugin: