Whether it's done by a government or Facebook, mass surveillance is still mass surveillance. But at least, with WhatsApp and Signal, only the metadata are observable, but not the content of my messages. It's still an issue, but something I'm willing to accept in exchange for a communication tool I can use with my non-technical friends, family, co-workers, etc.
Signal is the only one to trust for security, privacy and handling mass surveillance better than the other apps.