I think I was comparing Van Aert's third place on a mountain stage (which had two surviving attackers) to Cancellara's 20th place. And I think that is perfectly fair.Van Aert has shown a lot on the climbs this year. He has the possibility, if he wants, to try and become a GC rider in the future. Next year he can contend in T-A if the route is a classic one with an ITT and hilly stages. Maybe he can do a top 10 in some other week long stage race, but that's it for next year. And that's the way it should be IMO. He has to concentrate himself on the classics and of course that's his first priority.
Also comparing his 4th place in a ITT with Cancellara's 20th place in a road stage isn't exactly fair. You think Cancellara wouldn't beat his captain A. Schleck in a TT on the 2020 parcours if it happened 10 years ago? Probably would have also done a top 5 performance. Having said that, Van Aert has shown this year more climbing ability than Cancellara at any point of his career IMO.