The plagues that decimated the population were inevitable, and those destroyed much of the culture with no special effort by the invaders. Certainly any of thousands of variables would have led to different cultural outcomes, but the native population was so vastly outnumbered after the Old World diseases got done with them that their contribution to the larger picture of humanity was bound to be limited no matter how they were treated.

Ultimately, I don't see a compelling reason to think the world would be substantially different had the genocides not driven them to the brink of extinction.

Edit: to be clear and reiterate my previous point: the loss of culture is a tragic loss no doubt. I'm simply saying that there isn't any way to put a value on that beyond "we don't know things about this culture" which is somewhat circular. There are a lot of cultures we know almost nothing about that were lost to history because they died out or were assimilated. Knowledge is a worthwhile goal in itself, but to say it has any usefulness beyond the satisfaction of simply knowing it is a stretch.