As insufferable as Mess' love for Barzal can certainly be, no one can accuse them of retrospect and hindsight as far as Barzal is concerned - They were just as big a fan of them then, before the Draft, as they are now after Barzal's rookie season.
It's less an instance of hindsight and more someone being unable to stop talking about how "right" they were. (Given that the 2015 class is still very much undeveloped, I think it's too early to say definitively who will be better than who - Mess obviously would've been happier with Barzal, while most Leafs fans are, not surprisingly, thrilled with the Marner selection thus far.)