I'm not a Dak hater, but I'll answer the question.
Actually, it's pretty easy.
The evaluation is given based on what is AVAILABLE at the time.
For example, if Dak were playing in a league that featured, Dan Marino, Joe Montana, Troy Aikman, Jim Kelly, Dan Fouts, John Elway, Peyton Manning, Patrick Mahomes, Russell Wilson, Tom Brady, Aaron Rodgers, Drew Brees ... would he be considered top 10? ABSOLUTELY NOT!!!
Now, let's say he's playing in a league with Jameis Winston, Alex Smith, Kirk Cousins, Baker Mayfield, Vinny Testeverde, Trent Dilfer, Sam Darnold, Daniel Jones, Mitch Trubisky, Mac Jones ... would he be considered in the top 10? ABSOLUTELY YES!!!
What makes the difference? Simply put ... THE LEVEL OF QUARTERBACKS HE'S PLAYING AGAINST OR PLAYING WITH IN THE LEAGUE!
Currently, how many franchise quarterbacks are in the league? ... Rodgers, Brady, Allen, Jackson, Burrow, Mahomes, Wilson, Herbert. That's eight. So, of course, Dak would be in the discussion as a top 10 quarterback.
But what does that REALLY tell us? Probably not much given the talent above him and the talent existing within the league.
The issue really shouldn't be whether Dak is a top 10 quarterback. But, rather, it should be is Dak a franchise quarterback - one you can entrust to lead your team deep into the playoffs and take the game on his shoulders and win the dang thang - and that on a consistent basis.
Teams aren't looking for top 10 quarterbacks, per say. They're looking for franchise quarterbacks.
Until they find them, your search at quarterback will always be never ending.
Ask Kirk Cousins.