Instant messaging never really opened up. Jabber was a nice stab at it, but it didn't catch on. SMS is the closest we've come.

This is in stark contrast to email, where closed versions were made and struggled on but ultimately succumbed to the one open version.

I wonder what makes them different.

In the mid-90s, email was offered as a selling point by ISPs. ("Sign up with us and get 1/10/unlimited email accounts!")

It's also one of the easiest online protocols to understand and an obvious benefit. So ISPs sold it to the public and business. And because all the ISPs were unique but needed to interoperate, there was no proprietary format.

AOL and CompuServe soon worked out that access to external email was a thing, so they built gateways which broke their users out of the walled gardens.

ISPs didn't do the same for IRC. It was always more of a nerd toy, which meant the public didn't know about it. AOL and CompuServe (etc) had proprietary chat, and there were a lot of chatalikes like ICQ, and eventually things like MS Messenger.

Without ISP promotion none of them made it to the mainstream.

I don't think Facebook and Apple can kill the web entirely. There's always an "AOL niche" for a simplified social Internet. FB lives there at the moment, but it's a vulnerable slot, and unless they break out into something new FB will be dead in a decade or so - if only because teens will grow up using something else, and will stay with that something else as they get older.

Yes things changed; but from one small set of silos to another small set of silos. Things haven't opened up.