Python with click and PyYAML can go a long way - then you can build it as a CLI application and use the same from CI. In a java shop, picocli + graalvm probably. I wouldn't like Go for this purpose (against the conventional wisdom - because boilerplate and pretty bad debugging capabilities).

That said, if you absolutely need to use shell script for reasons, keep it all in single script, define logging functions including debug logs, rigorously check every constraint and variable, use shellcheck, factor the code well into functions - I should sometimes write a blog post about it.

There is a debugger for bash: https://github.com/Trepan-Debuggers/bashdb Not that I'm recommending 10k-line programs in bash, but a debugger is useful when you need it.

Shell is a very real language, and it has a debugger; it’s called set -x and/or strace.

Like I said, use something with a real debugger.