Functionally there isn't. Much that one would expect from a POSIX shell is fixed/broken depending on perspective. The migration path is significant.

In any case, this is all mostly moot. Since many (and many more to come) just use chatbots to write their scripts, ease of (human) coding for newcomers is increasingly a non-issue. If people install fish it will be because of the pretty colours and advanced tab completion. That may alone be enough to make it a useful replacement to people who will AI their scripts regardless of what language is in play.

- Evan