I'm not sure I so much believe in "ruining" players. Nobody really knows how guys would turn out with more/less time in juniors, it's all speculation. Most of the guys who make the team really early but end up busting might have done the same thing if they'd stayed in juniors. I mean, Seguin only got 12 mpg as an 18 year old last season, and was healthy scratched at times, didn't stop him from blowing up this year. If you have the talent/ability, you'll probably succeed eventually.
With that being said, I could see it playing somewhat of a role in terms of career path. If you're borderline talent-wise in terms of top 6 vs. bottom 6, but spend a long time in juniors/the AHL where you really play in a star role, and develop both offensive ability and confidence on offense, I can see it leading to more of a top 6 role, while if you play in the NHL before you're ready to you could get "stuck" just working on your defensive game, and never truly gaining the necessary offensive skill and confidence to play on the 1st or 2nd line.
I think Nino should be back in juniors right now, but at the same time I think if you're a truly skilled player, you will rise to the top more or less no matter what. Nino will probably play in the AHL next year, Turris-style, where he should get a chance to play a more prominent offensive role, and concentrate primarily on improving his offensive rather than defensive game. I don't think he's "ruined," but I do think he may not have had the highest offensive upside to start with, and this year probably has not been the best in terms of developing his offensive abilities OR in terms of his confidence in his ability to be an offensive contributor at this level.
Can anyone think of another top 5 pick who played 50+ games in their first true rookie season, while recording just 0-1 points? I can't think of any, forwards only obviously. Joe Thornton springs to mind somewhat, with 7 points in 55 games in his rookie year, but that's still a lot more than 1 point.