Signal "leaks" metadata because everything goes through their servers. They can't see the contents of messages, of course, but they can see everything else. At least to the extent that they have information about users. Simplex fixes this, that's what it was designed for.

That's a bit of a stretch. The only metadata that it actually "leaks" is the frequency of your messages and your IP if you're not using a VPN. The thing is, a VPN can hide the IP easily, the frequency of messages issue is going to happen with any messenger. With Sealed Sender, metadata isn't a concern unless you dox yourself. And if you do that, then that's on you, not on Signal. And even if you do that, sealed sender still makes it impossible for any snoop to actually see where messages are coming from. Thing is, even with other messengers like Session or SimpleX, if government authorities are paying attention to multiple contacts in the same circle, they're going to know who is actively sending messages, whether it's through Signal or one of those anonymous messengers. The only advantage to using an anonymous messenger is to speak anonymously with people you don't know in person. If you're talking to people over the internet and you want to stay completely anonymous, then it has a purpose. It's for the same reason that people say you shouldn't sign into accounts on Tor because it immediately de-anonymizes you unless that account is exclusively used on the Tor network. At the end of the day, using an anonymous messenger to keep in contact with people you actually know in person is not any more secure than using Signal. And that's without diving into the whole subject of SimpleX being run by a for-profit corporation instead of a non-profit organization, which is concerning in and of itself.