No one would have taken him top 10. That isn't the Russian factor, players improve rapidly, what about Sebastian Aho's improvement in that same time frame? Should he have gone over the 5th possibly. But, to say he's top 10 is just using hindsight to an extreme. His stats were good enough he should have gone higher than 10th, but to say he should have gone top 10 if not for bias towards Russians like what happened with Tarasenko and Kuznetsov is far-fetched. Yes, his KHL numbers at 17 were similar to Tank and Kuznetsov, but they were also similar to Maxim Kitsyn.
Sebastian Aho and Rantanen would still probably go over him. Then there are the debatable ones like Barzal, Connor, Boeser and Konecny off the top of my head. He's not even currently a lock for top 10.
Aho probably should've been like a mid-first round pick, and I'm pretty sure he suffered from his Liiga team only allowing him to play one game at the 2015 WJC18, but we are talking about a player who went 35. He didn't go 135. Its very possible teams might've had a 15-25 range grade on him, and they instead picked someone else on their list who might've still been available. Also, this was prior to the Finnish hockey revolution, so I do think good Finn's suffered in draft rankings compared to that of players from countries that were doing really well those years. It seems like Finn's now are rated a little more properly, and aren't as susceptible to being overlooked like Aho was.
As for Kaprizov, I'm sure he made some improvements, as players do all the time from one season to the next, but its not like he was some schlub who emerged from nowhere. I don't remember the 2015 all too well, but I do remember studying the 2015 draft, and considering him to be a high upside player that might be overlooked, although it was conventional wisdom that he was not going to go in the first round. That doesn't mean though that he shouldn't have. I'm sure if people studied his game more closely, they'd have settled on him in the first round, at the very least. His stats were really good, his potential was really high, and he was being compared to Sergei Makarov at the time. I would chalk this up more to teams getting his selection wrong than incredible improvements from Kaprizov. It might've been some of both.
I do think he's a lock for top 10. I think I'd have him 7th. If you'd instead have him like 11th or 12th, I don't know what the argument is here.