Isle Royale is being preserved today as a wilderness, but it isn't an "untainted" one, and hasn't been for a couple hundred years. It is what it is because of human activities.
As long as those human activities are merely that: human activities, I would still consider the island untainted in a way; there's nothing especially unnatural about most human actions, even if those actions often bear effects that might be described as a plague. This changes, however, when those human activities start involving actively trying to "shape" "nature", as is proposed by the ecologists this article is about. In my opinion this would instantly change the situation on this island from "nature trying to find a new balance after a small infection with humans" to "not nature anymore".
Through some strange feelings of guilt about the way it has affected nature in the past, mankind has somehow developed the idiot idea to try to keep the few occurrences of nature that we have left exactly like they are now. By doing that, we're slowly turning nature into a museum. Instead of doing that, we should have the decency to let nature be nature, even (or especially) when it changes in a way that we don't like.
This may (will..) probably mean die offs and those obviously aren't a good thing. According to humans, that is, mostly because of their somewhat irrational love for big mammals, cool trees and fear of change. But nature doesn't give a fuck, it doesn't consider humans special. The place will look totally different in 10, 100 or a few 1000 years anyway. Just let nature be and it will find a new balance. Maybe not on a timescale meaningful for the average human, but it will. Because that's what nature does.