He's about the same weight as Merckx was, but I accept the sport has changed massively. I suppose my point is that JA weighs less than the likes of Bernal and Pogacar, and whilst he's shown he's certainly decent in the mountains, he's other worldly at puncheur style efforts versus just decent at hour long climbs at altitude. I suspect MvdP is similar, as he's had decent results in LBL and Lombardia so can clearly climb, but it's hard to see him doing well in long climbs.
Froome was the opposite, as he never did anything in the hilly classics despite being up there with the best at longer climbs. You could also look at guys like Contador and Quintana in a similar way. Both excellent climbers but they've done nothing in the hilly classics.