Its like saying you are not buying steam games, you are buying pointers to those games. I would say that you are in fact buying games/art, but doing so in a closed environment/ecosystem. An even better analogy is buying skins inside a game

The marketplace you propose could be interesting, but IG already existed with a huge number of artists who’ve already had a following/status/lore. Also there is the exposure to a tremendously broader&bigger audience than any other platform could possibly have. Not saying that migration would be unachievable, but so much would be lost for something that I don’t see come close to being a compensation