I don't think anything got "shot in the end"; the protocols of old were often just reverse-engineered too. Few bothered publishing anything about it, which is why Jabber/XMPP was created.

Since then encryption made things a lot harder; specifically, E2E encryption. You can't "just" login to a server and send messages, you need to encrypt and decrypt things on the device with the right keys, and how do you handle things like message history WhatsApp and Signal solve this for the desktop/web versions by designating your phone as the only device that can connect to their service, and everything else communicates via that phone. Telegram solves it by having regular chats not be E2E encrypted, and having a special "secret chat" feature for it.