A Netflix spokesperson tells the The Verge that AirPlay 2 doesn't have digital identifiers that allow Netflix to tell the TVs apart, making it impossible to tell if users are getting a good experience when casting to those devices.
We want to make sure our members have a great Netflix experience on any device they use. With AirPlay support rolling out to third-party devices, there isn’t a way for us to distinguish between devices (what is an Apple TV vs. what isn’t) or certify these experiences. Therefore, we have decided to discontinue Netflix AirPlay support to ensure our standard of quality for viewing is being met. Members can continue to access Netflix on the built-in app across Apple TV and other devices.
So unless Apple releases an update to the AirPlay protocol it doesn't appear that Netflix will be restoring support any time soon.
This A Fight between Titans.
I can only see that money are the problem. Or bs between them for expanding the AirPlay (even though is not official though)
Netflix’s “making it impossible to tell if users are getting a good experience” translates as, ‘we can’t monitor users to market their usage data, and if we CAN’T abuse users, we just won’t bother!
Netflix is just like Amazon, Google and Facebook, despite their monthly fees, the consumer IS their product. There’s nothing free about the services, as the actual fee is your privacy.