So only art in museums is culturally significant? Made by artists who are dead? What about buildings? Religious places? Graveyards? Note that these are things I called out in my first comment so I’m not trying to move the goalposts here. You highlighted the Taliban destroying cultural places so, by your definition, we must include those and since we can’t displace any new ones must be added.

I completely disagree that the footprint of the world’s art museums is minuscule. Museums today already have problems with storage. In order to meet your definition for art, museums must continue to expand their collections. As the number of people grows, the number of artists grows, increasing the supply of art. How do you define “great artist” without proportionally increasing the number? As fields specialize, so too do the “great artists” that define mediums.

What about books? Records? Movies? How do we decide what to keep here?