We have, and we open sourced it :)

https://www.spinnaker.io/

Here is a blog post (2010) describing the decision to move out of our own data centers:

https://medium.com/netflix-techblog/four-reasons-we-choose-a...

To me, the most important part of Netflix isn't the encoding or compute parts, ( AWS ), but the delivery. And all of their delivery, networks are already done by themselves through Open Connect and OP Server.

So they already have their own system. As as some below have mentioned, they could simply move to Azure if they wanted without much trouble.

So Netflix now needs to hire and manage a huge infrastructure team that they don't have today. (Not to say they don't have ops folks but the incremental need would be enormous.)

That's not to say it might not be a worthwhile approach over the long run but it would be a huge strategic investment in something that has essentially nothing to do with what they view as their core differentiating service to customers.

Would Netflix have done things differently if they had known they'd reach this level of usage? Perhaps. But disentangling now would be very difficult and almost certainly disruptive--including a likely reduction in quality of service.

I'm pretty sure they do a lot of their own stuff, AFAIK, they run their own CDN, and then use AWS for everything else.

Why do you think they don't?