To be fair, I think Duchene always thought he was the savior--Hart Trophy candidate, 1st All Star Team Center, etc.--that would bring the Avalanche back to the promised land. It felt like he thought he should be picking up a point in almost every game and carrying the team on his back, even if he never had the talent for it. And when he couldn't, it was a failure. That discrepancy between what he was and what he thought he was would always cause things to snowball.Now that he's no longer in Colorado maybe he slides into that "simple" 1C 65~70pt center role.
I think that's why he celebrated his 30 goal season so much--he always envisioned himself as a 30 goal scorer. I think he chased numbers to an extent, not because he was that selfish a player but because he had expectations of himself that he had to meet. In seasons where a national team spot was on the line, he always upped his defensive effort as if to prove he was a versatile two-way forward that deserved to be on Team Canada. It meant a lot to him. He was never close to contention for any awards so I think it was a way that showed he was one of the best players on the planet.
He has all the tools to be a 1C even if his hockey sense is a bit lacking. There's a reason some hockey people such as Hockey Canada think (or at least thought) highly of him. There's a reason he made the national team ahead of guys like Hall and Giroux. There's a reason why Turris was never even in contention.
The one thing you can't really fault is that the effort is (almost) always there even if it's not always in the right place. Yes, he quit on the Avalanche the year before last, but there were plenty of years where the team quit way before him and he looked like the only player who gave a damn. Roy lambasted Duchene for celebrating his 30th goal in 15-16, but Duchene was easily our best player that year.
To a lesser extent he's like MacKinnon before last year, he's not really lacking anything. The hockey IQ might not be top tier but it's good enough and the physical attributes are all there. It's not really about effort, it's about the mindset. What is he? What should he be? What should he be focusing on? I think he had the wrong answer to all those questions. Can he find them at the age of 27? Sure, plenty of people come into their own at that age. Would I bet on it? No, but it's still possible.
That being said, there's always the inevitable physical decline to worry about. I think he'll always have plus speed but he's already lost half a step. The edge work is still there and it's still one of the best in the NHL but it's still a question of how much he can afford lose before it's too much because he doesn't have the hockey IQ to make up for it.