Be fair with your comparisons, Froome and Quintana were at their top level for a pretty similar period, Nairo was just younger when it started.You don't have to be an ultimate racer to get better results than Quintana, his last podium was in 2017 at the age of 27. Whatever talents he showed in the early days as a super climber haven't turned into the once predicted victories in grand tours. He's only 31 now. Froome, Nibali, Contador even Valverde were all doing much better than Quintana at the same age. A multiple grand tour winner who can't even win the KOM in a grand tour now let alone make the top 10 or win a stage. I can't think of another grand tour winner in recent times with that much talent that has dropped off so much so quickly at such an early age. Aru and Dumoulin I guess are part of a larger group of grand tour riders at the crossroads of their careers.
I think the advantage Carapaz has over Quintana is that finishing kick. Quintana at his best could ride people off his wheel up a steep incline, but he never had the acceleration that Carapaz has; it’s won him stages at the Giro and Vuelta, it was a part of how he got the gap in Tokyo, it gives him options, in attack and defending a lead, that Nairo never had.
I can see Carapaz winning a monument. Less so Quintana.