I find what he is saying to be accurate. For about 20 years prior to retirement, I installed acoustical treatment into various venues (lecture halls, class rooms, meeting spaces, churches, gymnasiums, auditoriums, etc.), In most cases it was to tame a highly reverberant spaces so speech was ineligible. I can tell you first hand that you could throw all the money you would want at a sound system, but until the room was acoustically corrected, it was a waste of money. As he stated in the video, but in a slightly different way, you're only as strong as the weakest link, and a lot of times the weakest link is the acoustics.
Now that being said, once the room is treated, a system can live up to its potential. Acoustics seems to be one of the "voodoo" items because it is not understood.
In the kind of work I was doing, it was a matter of simply reducing reverberation times from as high as 10 seconds in some churches, to 3-5 seconds in lecture halls. In the world of hi end audio, it is much more complex because you are dealing with imaging and sound stage, etc, and it doesn't take much to play havoc with both of the above and frequency response.
I suppose it is easier to throw money at equipment because the spec's justify "improvement", whereas with acoustics, it is a gamble into the unknown.

