At one time they had open registrations, so spammers were taking advantage and setting up shop there. It looks like the instance now has a sign-up application. I have unblocked them. Thanks for noticing!
This is a good opportunity to remind users about our Fediseer profile: https://gui.fediseer.com/instances/detail/sh.itjust.works
We try to keep our Censures list on Fediseer up to date with the sh.itjust.works instance blocklist. That way we can leave notes in Fediseer explaining why each instance is blocked.