There are plenty of alternative shells that don't suffer these problems. Posix syntax didn't win because it was better - it's the classic 'worse is better'.

> Old doesn't imply arcane.

Indeed so. For example, awk is about the same age but doesn't suffer the same problems.

> the shell syntax was never meant to be anything like a systems or application programming language

A programmable shell is not only like a programming language, it is a programming language. Systems tasks have some specialised requirements but, overall, scripting is programming. There is nothing in the problem domain that requires the posix string-substitution problems.

If fish or oil had existed back then, they would likely have won, since they are better.

I think Bash won as Bityard says above, in the sense that COBOL won, which was because it was everywhere (approximately) and then when another system was being built to do something in COBOL’s niche COBOL was the obvious choice. Once it was sufficiently established it won by inertia and absolutely not because it was the better language. Or maybe it was the better language in its time, but it certainly is not now. And note I’m only talking about COBOL’s niche, of mainframe-based processing in the banking, insurance, state and federal payroll and similar areas.

> It was meant to efficiently automate systems tasks.

Shell was designed to launch processes easily. Unix philosophy pushed to make every function an application. And that's ultimately what shell "syntax" is.

There's shockingly little syntax in the shell. A lot of what we think of as "shell syntax" is actually full blown (standard) programs which the shell is launching. My favorite of which is `[`.

What makes shell unique vs all other programming languages is it puts launching processes first. It has no friction there because if it did, it wouldn't work.

This is also what I think is gross about shell. Every other scripting language has at least some friction when launching other processes and that's usually a good thing IMO.

One of these are not like the other. Python is perfectly serviceable as a shell, to the extent that one could largely replace bash with the Python REPL if they wanted.