There's something profound in that people like almost average, but don't like average. There are two ways this is true: categorization and imperfection.

Everything subjective has genres, then sub-genres, that a smaller group of people like, down to the individual. If something is very popular and/or mainstream in its sub-genre it becomes popular in its genre, and if very popular and/or mainstream in its genre becomes popular mainstream.

Everything subjective has "guidelines" it must follow in order to be popular, and the genres and sub-genres have further guidelines. But it can't follow every guideline or it won't be popular. At minimum people become desensitized, also some stated "guidelines" are wrong and the inherent "guideline" is different, because people don't completely know what they like. Because people don't completely know what they like, there are also "rare guidelines" that nobody follows or states but would create something especially popular, and rare guidelines create new genres.

For example, music. Almost every song (even non-traditional) has these common components: 12-tone equal temperament, simple time signature, "melody" "harmony" and "rhythm", etc.. Jazz, rock, electronic, etc. and have their own guidelines. Perhaps jazz was created because jazz chords used to be a rare guideline. But no song, even pop music, follows 100% of the guidelines. At minimum, instruments don't produce pure sine/square/triangle waves, melody has accents or modulation, etc. And the most popular songs do something novel (either completely novel, or they take something novel from a less-popular song and do better in other areas).

So how does this relate to the age of average? People know what I said above. AirBnB hosts, directors, etc. whose art is a business know the guidelines, both reported from others and inherently. But they don't know everything, and in particular, they either don't know how to break the guidelines in order to create something better, or they do know a way but don't believe it will work. So in order to create something that is the most likely to be the most popular, they follow the guidelines. What they create is at a local maxima, OK but bland, because it fits nobody's niche genres and there is no imperfection. Over time, it becomes less OK and more bland because everyone else follows the same guidelines, until some trend-setter reveals new guidelines that break the old ones and are more popular, then everyone follows those.

In order to be more successful than "OK" you have to know how to break the guidelines and follow rare ones, and the less other people who know the rare guidelines the more you'll be successful. But this requires 1) rare knowledge and 2) risk.

If everyone broke more guidelines, the world would be better, because to any individual, even though there would be more ugly AirBnBs and movies, there would be a few that are better than those we have today. And anyone who followed all the guidelines would create something that nobody wants, because although if you averaged everyone's ratings it would rate the highest, it would always be below first place. But since most people are following most of the guidelines, if one person breaks them, they get a few happy customers and less customers overall, so they give up or go out of business.

The former system, where everyone is following different guidelines, exists when people first discover an entirely new genre, and don't even know what the common guidelines are. But it transitions into the latter system, because every time someone discovers a rare guideline that captures enough of the market, the option that captures the most of the market is to follow the remaining common guidelines. We as a society can transition back into the former system and would remain until someone discovers a new rare guideline, but that takes cooperation which we don't have.