Things like docker images and nix builds are sold as huge improvements on this chicken-egg problem, at least from a "keep it all in one language" perspective, but only if you consider a docker script (mostly bash) or a nix config truly not the same thing as a shell script that more or less initiates the same environment.
docker/nix abstraction layers have advantages but aren't always as portable as a shell script. If you need a docker engine, I think you'll still need a bash script to install that...
Nix is possibly even more "single command", often just a curl if i'm not mistaken, but still requires config and shipping a build somewhere, and you still need to run the `curl` command in a shell somehow. i don't see how "just use python" will ever fix the init chicken-egg problem.
POSIX mistake number 1: Bash isn't available everywhere, even when restricted to Linux. Even Debian avoids bash for a good reason (Bash is slower than most POSIX shell implementations), although it's installed by default for convenience.