I think its because we've been spoiled with Dahlin, Matthews/Laine, McDavid/Eichel, Mackinnon/Jones, exc. in recent years. He's above RNH/Hischier though, I'd think Hughes & Kakko would go #1 & #2 if they were in the 2017 class. (notwithstanding what we now know about Petey)
I don't think the later group is worse than previous years. It might even be better than last year TBH. Lots of good players from 2-15. This years NTDP class is one of the best ever.
Dach / Podkolzin / Turcotte / Byram all look like they could be '1st line' players, some people/teams might throw Cozens, Boldy or Zegras in that mix too. Then there's also Caufield & Kaliyev who have that upside but a bit of risk. Not to mention Spencer Knight who seems to be one of the better goalie prospects in awhile. (definite 1st rounder)
Beyond that most of the guys probably project as 2nd line players, but you never know. This years first round has good depth I think.
Everyone's list is different, but I'd say it goes till around #20 in prospects you can feel pretty confident projecting as T6F's / T4D's.