I believe the full docs page does indicate that there are binaries to install via popular package managers [1]
I'm not complaining for the sake of complaining, I'm saying if they want to play in the Big Boy leagues, they need to do things right.
If you're on Arch, gentoo, or openSUSE, you can use the package. It is true that Debian has not packaged jj yet.
It'll get there, and it's fine if you'd rather wait until things are more mature.