Just getting a few hundred yards away from the highway will weed out 99% of the tourons. They can't be out of eye sight of their vehicles. I've heard of many backpackers in Yellowstone going for days without seeing crowds once they get to the backcountry.
Yeah, that's true but not practical... we did a couple of 4 mile round trip hikes but if you've never lugged a tripod and 600mm lens through the forest it's a little hard to explain how unpleasant that is. Net result of both hikes? Hike #1: nada... not even a decent landscape. Hike #2: crappy shots of a different set of Great Horned Owl chicks and a parent and more than a couple piles of Grizzly crap. I was ok with the hike until we ran across one that was pretty fresh.
In Yellowstone, for me anyway, the attraction is the thermal areas. Speaking from experience you don't want to hike the thermal areas. Fact is, you can't without risking (A) being dead and (B) getting into trouble with the rangers. My first time there I took a short excursion and ended up sinking to my knee in 100+ degree mud. I was walking right on the edge of a river that was probably 35° and suddenly my leg was sunk in hot mud. I was sure I was burned since I was 30' from a fumarol. Nope... got lucky... but the mud sure did stink.