Whatever, I mean 3rd party access to messages, which includes both security and privacy.
Have you ever heard of Viber? Even though their chats are E2EE, there's an option to sync them from mobile to desktop, and it was available for more than a decade. Messages are not stored in a central location.
Signal just isn't good enough for anything serious. It's a rather simple and not a very convenient app, that is getting too much attention from privacy enthusiasts.