Messenger, Mail, and Teams would be absolutely crippled without background support and notifications. Maps would be somewhat viable, and I'm not familiar with White Noise.

Also, 'native parity' is a moving goalpost. At the point you get support for all those things across all platforms, what else has been added to native that you are now missing?

This isn't even considering the fact that there is no incentive for apple to play nicely without an anti-trust ruling against them.