He's just a bit shit. I think that's where the Mustafi comparison (which I assume was jokingly stated) comes from.
Really, Rugani is not a good player, and I think people who would be pleased with him coming, on loan or otherwise, have been duped by his past youth reputation and his current club address. Do a twitter or reddit search; the Juventus fans are begging to get rid of him. Like with any player there's always a small chance that he could end up proving everyone wrong of course, but it's very unlikely, which makes it a bad bet - especially when we need quality to strengthen the defence.
Fingers crossed that Roma will buy him and save us from doing something stupid.