Nix is probably the best way to get all of those things set up without shipping a whole distro, but there will be a bit of a learning curve. If you’d like something a bit easier to set up for development (still based on Nix), I’d recommend devenv.sh.
The purpose of having a web-based user interface is to enable remote installation using a web-browser, which I imagine could be a pretty common use-case for server installation. Since a web-based interface is necessary for remote installation, it makes sense to use the same interface locally instead of having two independent interfaces.