Steam is a closed-source product, and it’s not the project’s responsibility to test it or any other closed-source products that users might want to run on it.
If you want a finished product, use something that’s been released.
GNOME on Wayland, installed several extensions just by going to extensions.gnome.org (installed the plugin for my browser when visiting the site, and then added a few extensions just fine). Didn’t need gnome-shell-extensions-common for the ones I selected at random.
Video playback in Firefox on Youtube: Works fine. Didn’t have to install anything extra.
Default install seems to include Gimp, Libreoffice, and a few other relatively small things. I added Myrlyn (which, running it to do installation, I really like the speed),
It’s easy to be critical. If you have specific issues, report them. Don’t just say “it’s a mess”. How do you expect anyone to address the things you think are “broken” unless you actually report them?
Sure - I installed that as well and tried it out. My point was that extensions are easy to install, whether using a browser extension or installing the extension manager.