Marchand has been a top 10 player for 4 years running.
I don't think you could cherry pick any 4 seasons you wanted from Perry's career to make such a case.
Perry has the Hart and the Rocket and I understand that argument. Those are important trophies to win and he won them. But he also won nothing else in his career, topped 70 points 3 other times, and finished with a lone 13th place Hart vote across his other 14 seasons.
I'll even add that Marchand will almost certainly not win a single piece of major hardware in his career. However, for Hart nominations, he has finished 7th, 11, 5th, and I'd be surprised to not see another within top 10 vote for this season. He's also been getting respectable Selke nominations (in the 10-16 range).
He is 5th in total points and tied for 3rd in PPG over the past 4 seasons. He is 4th in total points and 6th in PPG over the last 5 seasons. McDavid, Kucherov, Drai, Crosby, Malkin, Kane. He trails, ties, or leads some combination of those players in both categories. MacKinnon slides into these stats when you shrink it to the last 3 seasons or less. That's huge and I feel like most people still don't realize it.
I still think Marchand has already surpassed him cumulatively and 2-3 more seasons of his play similar to his level over the past 4 years should make it clear for those who don't already see it.