We’ll never know how a fresh Remco would have dealt with Alaphilippe in that form; I suspect you’re right and if Colbrelli could sit on Remco’s wheel and out sprint him at the Euros, at the very least Alaf needed to only do the same to win Worlds.This.
It's a lot of fun to dissect the Belgian "strategy" after the race, but let's not lose sight of the fact that JA was simply unbeatable on the big day, with the WC on the line. Add to that a strong and motivated French squad with a proper plan.
I for one remain convinced that Remco could not have beaten Alaphilippe regardless of how the former rode the race. As I said elsewhere, JA was the only top-tier rider who could turn this last smallish bergs into race-winning moves. Brilliant ride by the repeat World Champ.
But that doesn’t take away from how Belgium’s tactics on the day ended up playing into Alaphilippe’s hands. France started sending attacks up the road early to make the race hard, so that Alaf’s attacks late on would stick against tired sprinters/rouleurs. And Belgium obliged them by not only putting men in those same breaks and driving them, but also by driving the chase behind as well, making the race harder and harder, and making their own sprinters (WvA and Stuyven) too tired to win sprints for minor platings at the end.