the skill level and physical traits needed to be an elite scorer on that level were still higher than before
I think we can overrate how much that changed while underrate how skilled Gretzky was.
Jean Perron said when Gretzky was just having fun in practice with the puck doing more circus stuff skating-with the puck, he never saw an hockey player more impressive at it in just raw physical skills, hands, hand-eye, etc..., when he was coaching him on Cup Canada/rendezvous 1987. Lemieux was on those team. He was just really efficient on how to get results that it was not always as flashy than some others ( a bit like some old heavyweight boxer knock people out on what look like nothing punch or old 2003 Mario was scoring a lot without big bomb shoots or much speeds anymore)
If Luka Doncic or Tom Brady were palyers from the 70s/80s we would find people saying they could not work in today world against the super athlete, Patrick Kane was not strong enough for today nhl, Ovechkin/Kucherov does not take it serious enough during the summer.
I think in some season of the nhl, prime Lemieux would beat prime Gretzky in a scoring race is a perfectly valid opinion, I mean the guy had 2.62 and 2.67 ppg season it is not like he was far in reality.
But peak Gretzky would, almost without a doubt, always be an elite player in any era, he would have find a way if the way he did it in the high-flying era did not work, he did find a way in all the juniors league he played in, the whl, the nhl, all the international tournaments rules and opponents style.
he did find a way in 1982 hockey, did find a way in the 1993 playoff, Art Ross in 1994, still going in the 1997 playoff, it was really not a small sample size era/league success story.
97-98-99 Gretzky assists total was one of the best versus nhl peers ever still at that point, 97-99 he had 32 more assists than the great Adam Oates, and kept up with peak Jagr-Forsberg 2 of the best playmaker ever.