[JdeBP]

> [...] shell is a mess and [...] the basic root cause of the mess is that you can not straddle interactive use and programmatic use with one language.

Note that some of the world has already taken this notion on board long since. About a decade ago, Debian Linux and Ubuntu Linux swapped out /bin/sh so that it was no longer the Bourne Again shell. Nowadays, as a result of this, one regularly finds Linux systems where programmatic shell scripts are interpreted by something like the Debian Almquist or Debian Policy-Ordinary (posh) shells and interactive login session shell work is the domain of the Bourne Again, Korn, Z, or other shells.

And of course, having a different "better" shell for interactive use was the reported rationale for the C shell.