Galchenyuk yes, he was 2PPG in Junior in his D+1.
Kotkaniemi no, he was overhyped (and I fell for it, seeing as I liked Bobby Smith a lot). Looking back, even in the training camp which had him make the squad, he did not produce that much offence.
KK had a pretty good rookie season, he just didn't grow from there. The habs terrible coaching and developing really didn't help.
It's not like he was in the league to learn and grow, he was there to be more effective than whoever else they could get and to make it look like the habs didn't make a pretty significant and ill advised reach. They still would have been worse off going consensus with Zadina. Kotkaniemi wasn't playing a lot of minutes and he wasn't given a chance to learn. He could play sheltered minutes, but the next year he couldn't cope with not being sheltered.
Kotkaniemi wasn't terrible, but he shouldn't have been 3OA and he shouldn't have been in the NHL until he was 21 or 22. He was described everywhere as a long term project, not as a guy who should be in the NHL at 18 (46th most points in an 18 year old season, even so).