If you're NVidia user you're justified to feel bad about this entire fiasco but remember protocols exist so that everyone implements their own part and users can mix-and-match and it works together.
If AMD and Intel can dedicate resources to maintain their Wayland implementations with no complains why NVidia can't?
> why Wayland developers don't want to write an adapter for NVidia's proprietary API
Because they could use the time spent on maintaining NVidia proprietary API adapter writing open-source software that will benefit all parties.