This is a stunning move. He's undoubtedly going to be on a few loan moves throughout his Juve career, with Serie A teams already interested (main one is Sassuolo). When he's not out gaining experience in a top 5 league, he's going to be training alongside Ronaldo at one of the best facilities on the planet with world-class coaching and competing for Juve's very weak left-back spot.
This is absolutely not a stockpiling transfer - there's a difference between this and, say, Issa Kabore. There's a clear pathway with Cacace, and if he doesn't make it at Juventus I'm sure he'll settle with Serie A, a league in which he's good enough to play a part in already without a doubt.