Coda is DEFINITELY not refusing to implement permissions. It is not a “simple and easy” thing to do as you claim.
Coda has been working on this for years, and the 3rd of four phases was announced here:
You can see in the look-ahead below that security is on the top of the list for 2025. It does not mean that it will be the first to be released, It is a very complex implementation to do.