> Most shells take less space than that!

Most shells dynamically link to a runtime your OS provides "for free". The 4.3 MiB binary in question is bundling the Rust runtime and its dependencies.

For reference, a statically-compiled C++ "Hello, World" is 2.2 MiB after stripping.

  % cat hello.nix
  {
    pkgs ? import <nixpkgs> { crossSystem = "aarch64-linux"; }
  }:
  
  pkgs.stdenv.mkDerivation {
    name = "hello-static";
    src = pkgs.writeText "hello.cpp" ''
      #include <iostream>
      int main() {
        std::cout << "Hello, World!" << std::endl;
        return 0;
      }
    '';
    dontUnpack = true;
    buildInputs = [ pkgs.glibc.static ];
    buildPhase = "$CXX -std=c++17 -static -o hello $src";
    installPhase = "mkdir -p $out/bin; cp hello $out/bin/";
  }
  
  % nix-build hello.nix
  ...
  
  % wc -c result/bin/hello
  2224640 result/bin/hello

For reference, some statically-linked shells on my system:

  2288K   /bin/bash-static (per manual, "too big and too slow")
  1936K   /bin/busybox-static (including tools not just the shell)
  192K    /usr/lib/klibc/bin/mksh
  2456K   zsh-static

For comparison, some dynamically-linked binaries (some old)

  804K    ./bin/bash-3.2
  888K    ./bin/bash-4.0
  908K    ./bin/bash-4.1
  956K    ./bin/bash-4.2
  1016K   ./bin/bash-4.3
  1092K   ./bin/bash-4.4
  1176K   ./bin/bash-5.0
  1208K   ./bin/bash-5.1
  1236K   /bin/bash (5.2)
  124K    /bin/dash
  1448K   /bin/ksh93 (fattest when excluding libc!)
  292K    /bin/mksh
  144K    /bin/posh
  424K    /bin/yash
  848K    /bin/zsh

(The reason I don't have static binaries handy is because they no longer run on modern systems. As long as you aren't using shitty libraries, dynamic binaries are more portable and reliable, contrary to internet "wisdom".)

Among the features it has: an interactive terminal GUI, threaded parallel directory walking, and git repository support. In around a thousand lines of code, total, including tests, half of which is the GUI.

I feel like that's just the result of having a native package manager making natural bloat and a compiler which hasn't had decades of work.

I think that’s a lame argument. First because it’s kind of a fallacy. Size is absolute not relative to something. Especially for software. No one thinks of software size primarily in the context of their disk space.

Further I think everyone keeps getting larger and larger memory because software keeps getting more and more bloated.

I remember when 64gb iPhone was more than enough (I don’t take pictures so just apps and data) Now my 128 is getting uncomfortable due to the os and app sizes. My next phone likely will be a 256