I'm just looking at whoscored, I know it's a bit fake, but still. How can you be weak in the air at 190cm? Also his overall rating is 6.74, which would be NOT BAD for a defender, but he scored 5 goals that gave him a high rating in that game and inflated everything.
In the non-scoring games Gabriel only had 7 games with over 7.0 rating. De Ligt had 16 such games.
Yes, arsenal is even worse than Juve, and he should get some valuable defending lessons here and most likely improve, but I don't know how much he can make key tackles, mark his opponent in the box etc.