The world has changed quite bit. If you have deep pockets and you can use AWS etc., it isn't a major problem anymore. However, if they indeed run it on their own data centers, that is impressive.
I think the performance of Netflix is highly dependent of ISP's data centers [1].
But yeah, there are still limits where the cloud won't help you.
If you whole infrastructure is designed to serve "historical" content instead of streaming, some bottlenecks cannot be avoided if you want to server low-latency sports stream. This came by surprise for me, but apparently betting has still significant role for the viewers.
The Open Connect Wikipedia page [1] currently claims 8,000+ Open Connect Appliances at more than 1,000 ISPs as of 2021, and OCA's in over 52 interchange points.
Netflix is shuffling data at a scale nobody outside maybe a dozen other companies globally needs to deal with, and I doubt any of the social media sites come close.