Right so IOW, not a single one of them had shown the least inkling of being a GT winner.
You probably haven't studied what it takes to be a World and Olympic pursuit champion....it makes you a supreme TTer. One that could do efforts at max, back to back to back. He also won titles in Scratch racing and probably killed it in Points racing. That would make him a seriously skillled and tactically gifted sprinter; particularly after very hard efforts. He also won the Junior Paris Roubaix so there's the Hardman credentials for you.
Fixed gear racing is a very serious test of limits due to no gear relief. You need to be strong enough to accelerate from slower speeds in the gear choice you plan to sprint at 40mph. The repeat efforts are great for hill thresholds. So Gerraint had shown
every quality needed to be a GT winner but was channeled into the Olympic medal hunt and won those, too. Lack of opportunity doesn't indicate lack of ability.
Remco would be the first to acknowledge that his family connections assisted nearly every step of his progression. Unfortunately they needed to step aside and let him grow as an individual athlete and IMO he's made that move.
Roglic is an irrelevant comparison and only on your list to denigrate his abilities I would bet. He is better than Remco in GTs now and can't be 21 again so no point in comparison.
Jonas is now the hero of Denmark but hadn't earned the pro ride to put him in GT supremacy.
Remco was anointed the Boy King of his neighborhood so his "legacy" was to be the TdF winner Belgium still is desperate for. Now his biggest supporters are hopefully embracing his potential as a
GT winner. Not
the GT winner. That's good. But to suggest anyone other than say, Lemond showed they could win the TdF at 21 is far from serious.