I think that in a thread dedicated to discussing government capabilities, it is reasonable to point out that the NSA almost certainly has capabilities beyond what the public is aware of or would expect.
Whether you should be concerned about them is a different story, but I’ll point out that nobody here seems to have suggested not using Signal or other apps because of this. I think that if you care about privacy and security it actually is important to have awareness of both historical and potential capabilities of the NSA and similar organizations, and I also think there’s no reason to believe the NSA has changed their behavior in the years following the stories linked in this thread.
These things can be true without preventing you from using what are still the best tools available, and indeed for most people even if you are aware of the potential capabilities of people like the NSA you can still ignore that when considering what to use, because most people aren’t targeted by the NSA to begin with.
Perfect should never be the enemy of the good, but at the same time I think we can acknowledge that good things out there (e.g. Signal) aren’t perfect.
I’ll reiterate another point made here for good measure: