The economics fundamentally changed a couple of years ago when cloudflare released R2. I don't know if anyone has built a streaming client for it yet, but R2 takes the largest expense (outgoing bandwidth) and zeroes it out.
Yor business would be wholly dependent on cloudflare. But if you don't have to pay for bandwidth, the economics aren't that bad.
(I ran a large porn site a lifetime ago, long before cdns were ubiquitous. If I was in the business today, I would absolutely put everything on R2 and make it work no matter how much client development it took)
You are missing compute aspect. R2 only solves the egress problem. YouTube accepts many formats and tries to stores them efficiently such that it makes seeking different timestamps in the video possible (and efficient). They perfected the art of encoding. Read about it.
I'm sure that infrastructure is valuable and useful, but might not be necessary. We had a simple encoder farm back in my kink.com days and it was a rounding error in our budget. I can only imagine it's cheaper and easier almost 20 years later.
Yor business would be wholly dependent on cloudflare. But if you don't have to pay for bandwidth, the economics aren't that bad.
(I ran a large porn site a lifetime ago, long before cdns were ubiquitous. If I was in the business today, I would absolutely put everything on R2 and make it work no matter how much client development it took)