Yeah, those ol' sound waves and reflections are a killer. A square room has similar peaks and dips is all dimensions. So the room induced peaks and valleys are all multiplied by each other resulting in much deeper valleys and much higher peaks. A non-similar dimensioned room might have typical peak to peak responses in the range of +/-20dB, most have less than that. A square room with all modes excited can easily exceed +/-40dB. You aren't hearing what's on the disc or what the equipment manufacturers intended when you have that much variation induced just by the room. With that much variation it's all but impossible to bring the overall response down to acceptable levels of flatness.
In the mid to high end of the frequency range, slap echo is multiplied and stays in the room too long which smears clarity, ambience and imaging potential. The only solution to slap echo is treating all of the walls, ceiling and floor with absortive materials which tends to then take the mid to high frequencies away all together. The room sounds too alive when not treated and too dead when it is treated.
One thing worse than a cube ... A newly constructed square room, on a pier and beam foundation, tiled, with a barrel ceiling and lots of windows without drapes.
Instead of a vaulted ceiling, the ceiling is shaped like the inside of a barrel. Highest at the middle and curved along the length of the room to form each side portion. It's a common feature in Dallas architecture of the 1970's. It belongs to the school of Bohemian Baroque Look How Much Money I Got design.
The only type of room I've been in that might be worse is a true geodesic dome. We had one at my undergraduate college which was actually designed and construction overseen by Buckminster Fuller himself. It had a ceiling which was constructed of curved glass panels. It was intended to be the University's chapel but it was not all that useable due to the mulitple long, constant reflection times. At some locations within the room you could not hear what was being said on the other side of the room 35 feet away from you. I had some classes that were held in the space and it was quite a treat to walk out of that space into an open field. A true lesson in acoustics.