This is an interesting topic for someone like me, someone who hasn't been to the Q in a very long time, and who traveled primarily in the BWCA for more than 40 years. Quite happily, I might add. I understand that things are changing now in the BWCA since my last trip in 2013, and not for the better, so my comments aren't "current", but this is my perspective from my traveling 1973-2013.
It has always been a bit puzzling to me that the Quetico purists "put down" those of us who go to the BWCA quite soundly because our campsites have fire grates and latrines. Because, to me, as I have been on this board and another one quite regularly for the past ten years, I have heard so very many discussions of "campsites in the Q", even "five-star", "four-star", and such--and discussions of the fire pits, the rather elaborate stone fireplaces (with photos), the logs around the fire pits, and the "improvements" at the campsites, etc., and I have thought, "Wait a minute! I was under the impression that the Quetico was totally unspoiled! That there WERE no established campsites, that you could camp wherever you wished, that there were no traces of other campers before you--that it was a true 'wilderness', not a 'park', like the BWCA!"

Believe it or not, I have never seen a rock structure in the BWCA. At least not one of more than five or six rocks. Now, I must admit I have not visited the famous "stone chairs" on Ge-be-on-e-quet, so those would be an exception to my comment. But I built a little Inuk once on Insula, and it ended up looking very foreign. It just doesn't seem to be done there.
Perhaps I am rambling and not making my point. To me, a biffy keeps the mess in one place and isn't a big deal. And a fire grate with a few rocks around it isn't much different than a big rock structure and "bring your own grate."
Are we kidding ourselves that it is a true wilderness? Sure.
But I guess my views are more like Mossback's. If I find it and it is sort of nice, I leave it alone. I just don't make it. When I made it that one time, I found it quite unsatisfying. I think I learned my lesson.