I'm not 100% happy about Signal being listed on switching.social, but it comes down to what the alternatives are for ordinary users.
XMPP is too difficult to register an account with.
Wire and Matrix/Riot are aimed at technical and business people.
Telegram seems to have its own privacy issues.
Signal seems to be the least worst option right now for a non-technical user, it's certainly better than Facebook Messenger or Whatsapp.