The number of something caused or created is not measure of complexity but rather of power.
Okay, perhaps you can say exactly how you are measuring complexity here. I was thinking that if you have twice as much of a thing, then that must be more complex. For example a 1000-piece jigsaw is more complex than a 500-piece jigsaw.
For parents, their sexual power and stamina determines the number of children. Though parents are not really the direct cause of the child. A better example is someone that designs cars, can only produce a large number of cars if he has the power to access a factory. So the ability to design cars requires greater understanding of complexity than producing large numbers of cars. Same with your example of the artist. The number of paintings has more do with his physical strength and stamina than his complexity.
But the artist's painting have complexity, right?
And you are saying he cannot produce more complexity than he has. So, while I agree strength and stamina are an issue, if you are right they will come a time when he hits his complexity limit.
Another example would be an AI that produces pictures (some examples here
). There is no strength or stamina involved, but they still produce images with complexity. Each AI will hit a point where it grinds to a halt because the complexity of the images it has produced has equalled its own complexity - if you are right.