Love Slafkovsky as a person and a talent, but his skating is a pretty big question mark that could scare me off from picking him in the top 3. It's hard to say whether or not his skating will really become that much better with age, since a lot of it is just down to sub-optimal skating technique. When I look at a forward prospect, I value hockey IQ and skating by far the most. While Slafkovsky isn't by any means a terrible skater or a bad playmaker, he isn't even close to being elite in either. That's a pretty big red flag for me.
Of course if his skating improves you could be looking at a really dominant player, but I think that's a little bit too big of an if to gamble on. Especially for an organization like the Habs, who desperately need a high impact player from the next couple drafts.