This is something I'm realizing as well. There's so much behind improving at the NHL level, it takes effort and dedication. You need to draft players with the right outlook, that aren't willing to sit on their strengths and ignore their weaknesses. It's why I like how much importance Habs management is putting on personality and character when selecting players to draft.
Look no further than Drouin and Yakupov. Very skilled with good skating but didn't improve since their draft year. Players with this kind of talent have an easy road in development leagues and they are shell shocked when they turn pro. Time and space is reduced and there are loads of big guys that skate well. Not many players to take advantage of as there is in development leagues. For every hit you can find, there are 3+ misses. It's a difficult job to scout and project development forward for kids at age 17/18.
Obsessive to improve is a huge development ingredient. The team can only do so much to facilitate their development. It's up to the player to put the work in. So yeah, if you want to be a pretend scout, try to find the guy that has the best D+ development. When I look at this group from 2-13, I see loads of good players. But then you wonder, it's not about who they are today, it's about who they become from age 18-23 and if they put the work in or not. Sometimes, a player thinks he's training hard but the question I would ask... is it considered work or do they enjoy it? The ones who are rink and gym rats are the ones who turn out well.
Look at the 2018 draft. Lots of people liked Zadina, Boqvist, Wahlstrom, KK, Hayton. Then you got the hits with Tkachuk, Hughes, Bouchard, Dobson. 3-12 in that draft reminds me of 2-14 in this draft. So many players to like but what will be the bust %? Will it be 25% or less or close to 50%? There is going to be some busts in this 2-14 range.... just hard to cherry pick them today.