The restrictions on creating art are the product of the society you live in, which means they are the product of capitalism if you live in a capitalist society. The way society is organised determines the cost of people's time, the cost of the tools, and the cost of the materials.
Yea I find when people say "ideas shouldn't be ownable" it's really the more general "deriving profit from private ownership was a mistake". Like you kinda point out, most of the reason I can think of that a person would want control of their intellectual property is to derive profit from it.
That reason has nothing to do with intellectual property or how it's created, it's a consequence of living in a capitalist society.
