Write Posix Shell
when the problem you’re solving is small, well defined, and unlikely to change, consider shell.
when the problem you’re solving involves linux, text processing, or managing files, consider shell.
What FreeBSD experience added to that is portability. I try not to use bashisms anymore (thanks to shellcheck), as POSIX is good enough. If it’s not, maybe shell is not the best approach for this problem. Portability and lack of dependencies will pay out eventually.