I was able to get the shell running in Firefox (for example, running ls or echo "hello"), but I think you are right that something is off when you try to install a package. Looking into it right now!
Some packages (like Python 3.6) are a bit out of date. We are planning to update most of them as languages add native support for Wasm and WASI. But yes, in general the packages are mainly community driven.
For example, you should be able to try irb / Ruby latest version here (thanks to their WASI support upstream a few weeks ago!)