I understand your anger, but I don't think that properly describes the situation. As a maintainer of an open source project your users are who you are about. If your users want support for bambu connect, then you are likely to implement it. Whatever Bambu does is whatever Bambu does, you need to accept it.
> Part of that is thinking about at what point the project becomes pointless as a meaningful BambuSlicer alternative.
Why would OrcaSlicer become pointless if it supports Bambu Connect? It also supports the Bambu network plugin.
> Everything is going to be inferior to using BambuSlicer. That is Bambu's real intent.
What would Bambu's motivation be to do that? I don't think they would have built Bambu Connect if the goal is not to support third party slicers to directly send things to the printer. Note that most 3d printers on the market didn't or still don't have integration into slicers.