This is why we need device to device encryption on top of all the security that a telco has. There is no excuse for any connection I make being unencrypted at any point except the receiver.
Stupidity and banality is a far greater threat than conspiracy.
Clearly, the counter-intel part of the US government effort has been less successful than the surveillance and intelligence gathering effort. But that doesn't mean that the US government wants all those other nations to be able to gather data from these systems. Our government wants nothing more than to be the only national government capable of gathering data from these systems.
Getting them to actually use them is hard, especially when the whole point of the app is to communicate with other people, and literally none of the people they regularly communicate with other than yourself use (or even know about) Signal.
End to end encryption has proven to be unworkable in every context it's been tried. There are no end-to-end encrypted systems in the world today that have any use, and in fact the term has been repurposed by the tech industry to mean pseudo encrypted, where the encryption is done using software that is also controlled by the adversary, making it meaningless. But as nobody was doing real end-to-end encryption anyway, the engineers behind that decision can perhaps be forgiven for it.
I'd say there's a very real use for this, though, which is that with mobile applications it's more complicated to compromise a software deployment chain than it is to compromise a server-side system. If you're a state-level attacker and you want to coordinate a deployment of listening capabilities on Signal, say, you need to persistently compromise Signal's software supply chain and/or build systems, and do so in advance of other attacks you might want to coordinate with, because you need to wait for an entire App Store review cycle for your code to propagate to devices. The moment someone notices (say, a security researcher MITM'ing themselves) that traffic doesn't match the Signal protocol, your existence has been revealed. Whereas for the telcos in question, it seems it was possible to just compromise a server-side system to gain persistent listening capabilities, which could happen silently.
Now, this can and should be a lot better, if, say, the Signal app was built not by Signal but by Apple and Google themselves, on build servers that provably create and release reproducible builds straight from a GitHub commit. It would remove the ability for Signal to be compromised in a non-community-auditable way. But even without this, it's a nontrivial amount of defense-in-depth.
As the article points out, there are many other adversaries to be concerned about. Protecting against them would be good. Don’t give up so quickly.
Aside - not the main point —>
I actually do not know if we are at the level of “forced speech” in the US. Publishing hacked apps would fall under that category. Forced silence is something and less powerful. Still bad, obviously.