I don't get this talk of dismissing Juventus as a serious threat. They are a tier 1 team, having advanced to CL finals twice and quarter-finals twice in the last 5 years. They have money. All of their CBs are old.
I think the players are a bit different from us fans, to most of them the No.1 thing is probably where they can get solid minutes, play and develop, instead of the prestige of the club. I don't doubt if we offer De Ligt the same conditions (say a guaranteed starting position) as Juventus does he will pick us for sure, but if Juventus keeps enticing and promising him with a guaranteed starting position while we can't (obviously we can't and shouldn't), he might go there just for that alone.