Dorofeyev and Denisenko are born only a few months apart so they are the same age basically (which is how you confused it, I assume) but they are in different draft classes which should have become obvious to you while writing the second statement here.
In any case, I don't see the point of this fixation to Dorofeyev. You wrote it, you double-downed on it, what's the point. How is this or why should it be Denisenko vs Dorofeyev? One of the reasons he slipped likely is his very early birthday but it has nothing to do with Denisenko whom we can compare to any number of players. I'd say Kovalenko is by far more relevant comparison at this point as they are playing on the same team and he is being trusted to play in more situations and is now ahead in points, even.
Having said that, your point "everybody and their mom thought/think Dorofeyev is a better prospect" is clearly not what his coaches think as neither Jandac nor Vorobyov actually give him a real role on the team. Not only that, national team coaches as well. Denisenko lead WJC team in scoring, while Dorofeyev didn't even make the team. So "everybody" is not the scouts and not the coaches. I'd say those are 2 quite trustworthy groups when it comes to player evaluation. While Loko actually puts a pretty big emphasis on giving opportunities to Denisenko for 2nd year in a row not to mention his NT accomplishments.
P.S. Guryanov or Trenin probably shouldn't have been drafted 100+ positions above Kaprizov either, for example, but not like it matters, those things happen for multiple reasons and kinda aren't relevant one to another. You can definitely see why Denisenko went so early, you definitely make a case he shouldn't have, you can make a case the gap between him and Dorofeyev, or Kovalenko, or many other prospects shouldn't be that big, in hindsight. But it doesn't matter now.