Disney is a gigantic media company and has been streaming for years via ABC, HULU, ESPN, and other divisions. They also contracted to do streaming for companies that they didn't own, just handling the tech side. Almost certainly they have tons of data.
I distinctly remember ESPN started streaming online (and charging for it) years before Netflix.
So the "new" streaming service should really be called an "additional" streaming service, this time with Disney branding.
We're not talking about the same data. ESPN has been streaming since 2009, from what I remember, and it was bad then as it is now. I used Hulu for 8 years before dumping it. The quality just isn't there. ABC streams, even when logged in and the highest stream option chosen, still doesn't supply a video stream that's as clear as what Netflix can without interruption or video clarity going down.
The only thing Netflix is focused on is delivering quality video whenever possible and producing some shows. Netflix constantly spends money to make more money in terms of tech and the technology behind delivering video as clear as before with a smaller footprint both in data transferred and energy output. Disney is a conglomerate, and using its subsidiaries as example is useless.
As far as Prime video goes, Prime Video is just good all around. I'll give it 3-4 years before Disney realizes it isn't as easy as they think it is.
FWIW, I had 100 Mbps internet back in mid 2009 and it's gone up in speed since then. I've never had an issue with Netflix. A quick query has Disney getting $15B to invest in streaming services, this is prior to media which they own, and which I'll avoid for the sake of this post. This is before transmittance (bandwidth) costs and fees to implement CDNs at various backbones across the nation if not the world. Netflix spent $8-10B on content alone in 2018.
I have little faith Disney can upend Netflix and become the dominant streaming service. Netflix spends on itself as a technology company first, then a streaming company. Disney is a whole mish-mash of stuff. Disney could have taken out two birds with one stone by buying Netflix. They could have, in cash no less.
The only way Disney may succeed even while losing money on this service and offering a less than stellar streaming experience and struggling would be to offer their entire catalog spanning the beginning to now for subscribers. The reality is they won't and it'll be just as pick-and-choose as any other mediocre service.
That's with a lot of their old material being remastered to be able to stream at 720p or 1080p as a minimum quality level, without streaming snags or slowdowns currently present on their services via ABC or ESPN. And offering 4K to 4K Ultra HD with HDR where available at minimal extra cost to subscribers.