Every other argument for AI generated art is how people who might know how to write a good story don't have to learn how to draw and so on. Basically, how AI is abolishing obstacles in your way and not creating them, but there is one enormous obstacle that artists face even when AI is not introduced yet and that's competition.
Competition between each other won't be a problem, but the biggest problem is “unequal competition” where one party has resources to increase its marketing and popularity. This group doesn't care about additional “poor” competition because they will still be playing with other rich companies and the new competition will bury each other.
There are many other factors that may surface in the future for example people may enjoy “human created” art more but still this will reduce the requierment for skill of an artist which could be attained by practice and self improvement and it'll put more weight on wealth inequality.