What is a great room, what is a bad room? I've recorded in underground water reservoirs with over 20 seconds echo and recorded in rooms that have produced 1000s of gold records, at the end of operating jet engines and in opera houses that were reserved for royal invitations only over the last 35 years and I can tell you some of the most popular rooms for recording sound very strange. The playback room shouldn't add anything, closed headphones do a good job of showing the proper vision of the mixing engineer and that's about it. How can a listener judge a recording as if they were all the same? Some engineers care some don't and all of them are working with a budget, there is no standard recording sound studio so how can there be a standard sound in a playback room. After you hear a song you are very familiar with your brain will compensate for the acoustics in about 5 seconds in whatever room you listen to it in.