True, but a city of "artists" is also a monoculture.

Less so, because in reality most "artists" actually end up doing normal jobs to make a living in a variety of fields and just keep art as a side interest. A city of hobbyist programmers wouldn't necessarily be a monoculture either.

In current realities that's probably true. I've read about a city (town) of artists in post WWI France, which was dominated by Americans who moved there to pursue their artistic interests (painting). They were regular American folks, but thanks to the wealth disparity between USA and France at the time, they were basically wealthy by French standards, which allowed them to live a life of leisure and do nothing but paint. In that city, there were the dominant part of the population.

In practice, it becomes an artist/yuppie duoculture within a decade :)