While criticism of Zadina and pointing out he's not NHL ready is entirely fair, people also need to take a few things into account. He's 19. He undoubtedly picked up bad habits on a powerhouse Q team. He's still physically developing. He is known for both being a hard working in training and very self critical.
Its clear his confidence is down and that he's confused in his game trying to adjust from a junior scoring machine at a level he found easy to playing Men's hockey at the elite level. Different players transition at different rates, dependent on so many factors.
One thing I hate about sports forums is when people compare some kid to some limited full time adult player, without taking into account the massive development curve that can occur in the intervening years. Of course, no one can predict how a player develops during those periods unless they see him in real detail and very regularly. This kid has a boat load of skill and is often complemented on his work ethic. What he doesn't have yet is real explosiveness, strength or an awareness of how to translate those gifts to the Pro game without overthinking and overtrying.
He looks to me like a player who IS trying to correct his weaknesses (or at least improve those areas), and is massively overthinking things to a point of slight paralysis, which leads him to falling back into instinctive bad habits to try and shake himself out of his sense of underachievement. The way the organisation are talking about him seems to be a mixture of tough love for the bad habits but faith that he has the skills to be a big time player in the future.
If he was 21 and still showing what we've seen this summer/autumn, I'd be closer aligned to those showing serious concern, but he's 19. Most 19 year olds, even drafted in the top 10 just aren't ready at 19, even with more linear development paths. Lets not forget his numbers to date and his impression of having his whole game together are incredibly similar to Mantha at 21 and a bit.
Also, you just can't predict how a player will take steps forward at this age. While he could end up being less disastrous Yakupov, he's already achieved more in senior hockey (and in some cases more in junior) than Hertl, Huberdeau, Elhers, Dylan Strome, Timo Meier, Nino Niedereiter, Kadri, Brayden Schenn, Kyle Turris, Voracek had at the same age, and similar levels to Nylander., most of whom were picked at similar levels in the draft.
Looking at other recent high picks, he's shown more end product than Tippett, the ever broken Vilardi, Lias Andersson, Hayton, and is comparable to Cody Glass and Necas at the their D+1 age.
Now, right now he doesn't look likely to explode in the way some of those guys did in their D+2 year, but at the time neither did some of they. And he's definitely in a better place now than Meier, Strome and Ehlers were a that point in time, and we'd probably be happy with him reaching their current level of production by the same age...
Not saying it will happen, but drawing too many conclusions at this stage is stupid, particularly given how many other players looked brilliant in the Pro game at 19 who you wouldn't currently give up more than a 3rd round pick for.