I completely agree that every company having their own streaming service is unsustainable, and I suspect a lot of companies are going to be pushed out of the space eventually.

But there's a big difference between subscribing to 12 different streaming services, and subscribing to two or three. Streaming isn't like going out to a restaurant, where if you choose one then you're not going to the other. There are already plenty of people who subscribe to both Netflix and Amazon Prime, I don't see why there wouldn't be people who would subscribe to Netflix and Disney+, or Amazon and D+, or all three.

Besides which, Disney's content appears to be almost exclusively franchise-based and very exclusively family-friendly, whereas Netflix provides a much wider variation and a lot of darker, independent, or foreign-made content that you'd never see on Disney. There are going to be a lot of people who don't care to solely watch Marvel and Star Wars stuff forever, even if they subscribe to it for their family.