Well you only have to reinstall if you had affected versions installed.
For e.g. Debian stable, thats not the case. Or e.g. Arch sshd doesnt link to xz, so thats not a concern there.

Most systems wont be affected because their sshd doesnt link xz, didnt update to that version yet or simply isnt accessible from the outside.
Though it does show how vulnerable critical packages can be and how much better we need to protect them.