agree, but still backdoors sometimes leak to the internet. The companies who store data centralised like messeges usually have a big legal pressure like Telegram while it had system Ton. Idk if Mozilla have that sort of pressure, I would not question it if it would be decentralised system. Anyway there are always compromises and it souldn't be too much focus on it. For example basically all programming languages are have closed source parts, simply because CPU scheme is usually proprietary and could not be checked after manufacture.
- programming language -> .... -> programming language -> assembler -> CPU scheme
There exist another simplification then. A lot of meals can be cooked once and freezed after. It could be stored for months and warmed in a microwave in 6 minutes. However some products like potatoes should be mashed as otherwise it looses taste