Signal was absolutely up to the task of journalism in danger, 100% would recommend to everybody ('cos the bigger the network the better) as just a daily messenger
This is really critical. The privacy of Signal users is significantly enhanced by the fact that tens of millions of people are sending mundane traffic via the same servers. Doing traffic analysis on this is hard.
It's also helped by the fact that this includes the people using it for sensitive things. If you use Signal for talking to journalists and WhatsApp for talking to everyone else, it's easy for a passive adversary to see that you're doing something unusual.