I'm friends with Elliott Federman, the mastering engineer who used to be the head honcho at Atlantic Records, and he said the same thing in regards to room treatment. He hangs a carpet behind his head to stop reflections from the monitors getting to his ears, but otherwise, he just scopes out good sounding rooms. I suppose if your room is small and terrible sounding, you have no choice but to treat it, but you'll always be better off with a great sounding room to start off with. I think most engineers who denounce room treatment are the ones who have millions to spend on a studio in the first place.
The truth of the matter, is as long as you KNOW your room, and the monitors you're working on, you can always churn out good mixes, because you know what material is suppose to sound like in your mixing environment.
Many argue it's silly to make a record that sounds extravagant in a perfectly treated room, because unless your listener is a pro-audio peer, they will likely never be in a listening environment that is anywhere near flat.
I know treatment has helped me a lot, because of my room placement and what I have to deal with.
Bass traps are a must... period.