IMO, effective "scripting" just means the ability to solve ad hoc problems easily by writing task-specific glue that delegates the hard parts of the program to (1) an effective set of libraries you've written yourself and (2) external code or tools when it makes sense.

From this perspective, the languages of the glue, the libraries, and the external code all matter less than the ease of writing the glue; interfacing with the external code; and maintaining the libraries. The best language for this probably comes down to a combination of what you're comfortable writing (and reading, and maintaining) and what kinds of tasks you're trying to solve.

For me personally, using Python glue and libraries strikes a pretty good balance here. Writing a script "in Python" doesn't mean you need to reinvent the wheel. If you think `parallel` provides a better interface for map-reduce parallelism than `subprocess` (or than a library function you've written on top of `subprocess`), no problem: you can just call `parallel` from Python (and you'll probably find yourself writing a library function on top of it to abstract away the fact that it's a shell script).

But if you're much more effective working in Bash than Python, then writing your glue and developing your libraries in Bash could be the way to go.