You are missing that movies are not primarily paid for through direct sales and micropayments. Movies have an extremely complicated system of distribution to many audiences and through many media. The point of this system is to maximize producer revenue. If they don't do that, they can't afford to make movies.
US movie studios are reasonably good at making movies. They are maybe not so good at translating them into Chinese, figuring out how to market them in China, and distributing through the many channels there (first-run theaters, second-run theaters, VOD, DVD, streaming, and probably more). So they sell distribution rights to other companies.
If you want to replace that, you have to come up with a system that is better both for consumers and producers. Yes, hobbyists have figured out part of what's better for consumers. (Although those technologies are terrible compared with Netflix, so only a part.) But optimizing for one criterion is way easier than optimizing for two or more.
What hidden complexity am I missing on the delivery / payment side?
Not speaking of making content free, but making content easily accessible, at a nominal price.
The easily accessible part has been proven solveable, by hobbyists, already.