Why doesn't Joker train in the off-season with Hakeem or some other great defender to improve his rim protection?

Joker's getting dunked on a lot recently for his lack of rim protection during the Wolves match, but I think even critics would agree he's one of the most intelligent players in the game who has constantly improved every year from his initial SRP rookie status.

So my question is, why doesn't he spend the off-season learning from one of the greats and improve his defense at the rim? Seems like he'd pick up some basic tips that'd go a long way in the regular season at least.