With the increasing world population, tyranny of the majority sets in for many things, including music,
The music that the most people like, regardless of its quality, will tend to dominate the music scene.
For example, when the world population is 100 000, if 70% of the population likes pop music, while 30% like classical music, the difference is not that big. (70 000 vs 30 000).
But when the population grows to 10 billion, with the proportion remaining the same, the difference becomes rather humongous. (7 billion vs 3 billion).
Obviously "money-minded" music publishers, composers, and musicians will choose to be associated with pop music, leading to a vicious cycle. I.E, with the majority of the music composed being "pop", the musicians have less choice in their repertoire.
Note: This is a hypothetical situation only, so please do not be offended by it. Furthermore, the proportion is an overestimate -- I would hypothesise that the ratio is more of 9 is to 1.