Yeah, maybe its just me but I would argue that he didnt developed much or progressed significantly this past year compared to the previous one or two, but maybe I remember mostly his blunders, havent paid that much attention to Milan anyway. Compared to the other goalkeepers his age I dont really see someone exciting and with great potential so I guess its fair to qualify for that list. Maybe Lafont, strange that he couldnt make it in Fio but he is having a very, very nice season so far for Nantes. Just checked his stats - in 9 games in Ligue 1 he`s got 6 clean sheets and conceded a total of 5 goals, on paper thats way more impressive than what Donnarumma is doing. The rest - Dragowski is fine, Meret and Radu seem solid when I look them, and that Man Utd kid that plays in Sheffield is considered a major talent last time I heard about him, never seen Lunin play...
Also that list is too long, like you said, half the players are starting for their clubs on a very high level, few of them are already established and key players, the other half is like someone went to Football Manager and added those with "wonderkid" description to fill the chart. Some of them have barely played, cant be an adequate competition for the obvious top 5-6 players.