I've been working a lot in fairly complex shell scripts lately (though not long— not much over 1000 lines). Some of them are little programs that run locally, and others drive a composable cloud-init module for Terraform that lets lets users configure various features of EC2 hosts on multiple Linux distribution without writing any shell scripts themselves or relying on any configuration management framework beyond cloud-init itself. With the right tooling, it's not as bad as you'd think.

For both scripts, everything interesting is installed via Nix, so there's little reliance on special casing various distros', built-in package managers.

In both cases, all scripts have to pass ShellCheck to "build". They can't be deployed or committed with obvious parse errors or ambiguities around quoting or typos in variable names.

In the case of the scripts that are tools for developers, the Bash interpreter, coreutils, and all external commands are provided by Nix, which hardcodws their full path into the scripts. The scripts don't care if you're on Linux or macOS— they don't even care what's on your PATH (or if it's empty). They embrace "modern" Bash features and use whatever CLI tools provide the most readable interface.

Is it my favorite language? No. But it often has the best ROI, and portability and most gotchas are solved pretty well if you know what tools to use, especially if your scripts are simple.