Once you have this, this means there now two nodes which need to be coerced to compromise the system - endpoint software provider and communications provider. Well, actually, just one - the endpoint software could just be changed to use a different, compromised communications provider (I think you were envisaging some more subtle compromise of ciphertext above).
This can be fixed, however. A lot of the work Linux distros have done around reproducible builds, and the new focus on release transparency, is informative here. You could absolutely have a FOSS project with a release process that requires multiparty signatures of releases with the release signers in different jurisdictions, and requiring proof of logging to a release transparency log, etc.
I suspect a lot of pushback on this is because the implications are significant, Emperor's New Clothes and all, but fixing this sort of thing is the first step to solving the problem. Pretty much the entire internet community was in a mindset of "but government wouldn't ever do..." complacency before Snowden, despite increasingly blatant warning signs, before people were forced to accept that reality. (The reason is simple; it's a funny thing about humans, when they realise some fact X being true would be very materially inconvenient to them, their first reaction is to argue that X isn't true, as though reality is negotiable...) Having an accurate view of just how impaired our security model is in this area is the first step to making things better IMO.