This study is bogus because it has as its basis two values assumptions that cannot be taken as objective truth:
1) More complex chords in more complex combinations is better than fewer chords in fewer combinations.
2) More timbres is better than fewer timbres.
To address 1. If this is true, then the entire genre of the blues is all crap. But it isn't, people have found lots and lots of new and interesting things to do and to be invested in with the blues for over 100 years. And the blues uses 3 chords in a very precise formula. Indeed, there are a lot of popular genres that fall in harmonic formulae. That doesn't make them bad, or less good than the alternative. Also, the idea that pop music is less harmonically complex than the 50s is ridiculous. All of Doo-Wop had the same 4 chord progression. The vast majority of the R&B and early Rock'n'Roll tunes used the 12-bar blues. This is bogus and I suspect there is some seriously suspect methodology going on. This is also ignoring complexity in elements other than harmony and timbre (for example rhythm or stereo placement). And it is ignoring the value of simplicity or minimalism.
To address 2. How are they categorizing timbre? Because since the expansion of electronics we have a lot more timbral resources. And anyway, just because you don't have a lot of timbre doesn't make you bad. For example. 1960s folk music. Most often you have only a guitar and a singer. That's two timbres. You might be able to alter the guitar's timbre by changing how close your right hand is to the bridge, or alter your vocal timbre...but that is still pretty basic. And folk music is a) something old and b) well loved by a lot of people.
Music is comprised of many, many different elements these scientists are focusing on a very narrow set of them, with preconceived subjective notions of what makes something better than the other. There is no attention to genre or musical/social function.
Trooper6, Professor of Musicology