I feel the need to push back on this perspective.

Old doesn't imply arcane. It instead can (and does, in this case) mean that it won out over the course of decades against other less worthy alternatives.

Although you can write "programs" in sh, the shell syntax was never meant to be anything like a systems or application programming language. It was meant to efficiently automate systems tasks. It is kind of like the fork lift of computing. It does it's job very well, is bad at doing anything else, yet no other kind of vehicle can do it's job nearly as efficiently.

Comparing the shell to C, Go, Rust, Python, or JavaScript is crazypants. It has a different job than those, so of course it will look and feel different!