Well, you can't be drafted 4 oa on a deep draft without having great talent. Just like Drouin. How old is Drouin? And he is just beginning getting to his real potential.
Droin showed his real potential in the playoffs of 2015/16 where he scored 14 points in 17 games ranking 3rd on his team. Followed it up with 53 in 73 the next year. He was 20 yrs old in 2016. I point this out as a matter of fact and not to discredit Puljujarvis' potential.
As far as trading him for Hudon, as the centre piece, any GM would be a fool to do so. Puljujarvi is 20 yrs old has excellent size, good skater, and good shot but needs work on his decision making and his defensive play. Late bloomers aren't that common but do exist, St. Louis and Robert Lang come to mind. Got to give him a couple more seasons before you discard him.