So you're telling us right now that a season after both Siemens and Elliott were drafted, you knew that they'd both become non-NHLers? Or are you just using revisionist history to further along your point.
In general I take the approach that most prospects wont make it until they show something special or that they are at a point where they are so close that busting would be unlikely. I keep in mind the standard development windows for each role, so forwards you give a year or 2 and then see where they are at, dmen you generally wait until they are 24ish and goalies are complete random nightmares that I avoid entirely haha.
As of today I feel that Makar and Timmins are NHL ready right now given their skillsets in the 10-15ish games of theirs I have watched over the past year. Most fans don't watch a lot of junior/college games and aren't comfortable with those statements until they see them in the NHL, which I can understand but that isn't the case with me personally.
Kaut is another good example. I would feel comfortable assuming he will make the NHL because he is already so developed he doesn't have much room to go to at minimum make the league. Where thats at who knows.
Everyone else in the system I'd wait and see, including Kamanev who would also be pretty safe.
In general though I'm a pretty big hater of prospects. I never thought guys like Siemens and Hishon would make it and when I say that I mean while many fans took the stance that they never got the chance, mine was that they simply weren't good enough to get the chance and they never made it. Rooted for them, but didn't believe in them.
Finally I would say that Elliot is a poor example, mostly because offensive defensemen are one of the most boom or bust positions in the NHL. They either are incredible or flat out dont make it. You have to have an absolutely absurd skillset, like a Makar, to have any sort of confidence what so ever. If there was a position I hate on the most it would be that. I think guys like Jake Bean, DeAngelo back in the day, are all busts and am generally a hater.
Tldr: I assume prospects wont make it and make adjustments as time goes on.