Basically this. I don’t assume that just because it’s E2EE (or says it’s E2EE) it’s privacy safe.
Unless maybe if it’s my own system on both sides, running Linux, connected through some FOSS VPN I’ve set up myself, chatting through nc tunneled through ssh with a 100% silent wired keyboard, no monitor, no network, and everything powered off. Inside an underground lead bunker.
That doesn’t mean I don’t use Teams, Whatsapp, Gmail, etc. I just don’t assume it’s private.