We build Signal in the open, with publicly available source code for our applications and servers. To keep Signal a free global communication service without spam, we must depart from our totally-open posture and develop one piece of the server in private: a system for detecting and disrupting spam campaigns. Unlike encryption protocols, which are designed to be provably secure even if everyone knows how they work, spam detection is an ongoing chore for which there is no concrete resolution and for which transparency is a major disadvantage.
Threema is centralized as well and it’s also paid so I would say it’s even worse than Signal to be honest.
Paying 2 bucks in return for server coasts one single time is not paying… it is more a donation to keep the lights on. Server simply are the expensive part.
You defend already Signal above which is centralized too. So why you defend one system and not the other. Makes absolute no sense. Besides that, Threema plans to open source their app on F-Droid with code. If they also one day open source their entire code, you can theoretically self-host it for your own group or organization. So you give up on things way too fast and underestimate things. I bet you said 2 years ago, stop using Threema because it is closed source…
Theema was more transparent with everything than Signal. If someone gives me 50 Mio. and I cannot even establish my own server structure or open source everything, I would question the entire team, myself and I bet people who funded me want their money back.