You should still be able to cast from your phone or tablet to older Chromecast or Google Cast devices if you're on an ad-free plan.

Netflix has removed support for casting from its mobile apps to most TVs, including Chromecast with Google TV and Google TV Streamer devices. Casting will now only work on older Chromecast models ...

Casting is pulled from the Netflix app to newer Google TV devices You now can't cast at all on an ad-supported Netflix plan The change came without warning and hasn't been explained Netflix has ...

This is per Android Authority, which reports this morning that Netflix has quietly eliminated the ability to cast shows and movies from a phone to Chromecast with Google TV, Google TV Streamer, and ...