Not OP, but I would say that we, regular Bash users, don't really write complex programs in Bash, even though it depends on what you call "complex". Some of our programs can be pretty long, and we can do more within Bash than some programmers know (eg. the arrays/associative arrays features, the vast parameter expansion options etc.), so no, we aren't bound to some 100-line-max rule, if that's what you had in mind.

Bash (and other shells) are very good at working with other programs and using the filesystem. It's true you have to know many idioms, but once you're there, you can be quite productive for these kinds of tasks.