Something similar has often happened to Roglic. In races like Emilia, he was very strong, but in Lombardia, not so much because of the mileage.
Vingegaard began to falter in the final kilometers of Lombardia in 2022.
But especially at the World Championships, he'll find himself without Visma's support. Vingegaard is a cyclist who has relied heavily on the team. Although, as I said, Denmark isn't as bad as Slovenia.
A World Championship is nothing like a stage race. Just ask Froome: six World Championship appearances, all DNFs due to poor results.