There's a lot of these comparisons, and I wouldn't want to reply to all of them, but will on this one.
What's missing on most of these are the social aspect. With Google, you can't just drop into a 'miamidolphins' chat room to discuss the Dolphins. Nor can you instant message folks.
Think of what you'd need to recreate all of it with what we have today. Discord for chat rooms. Whatsapp for IMs. Chrome for browsing. Outlook for email. Steam for games? And there's many more features missing still. All in one application.
Further, part of the 'magic' to me was that the application itself was native and static. So you always had your menu bar to click between. And each clicked thing was its own subwindow. Like an OS inside an OS, if you will. Sounds wacky, but I loved the experience...at least at the time.
This is one of the main reasons why voice control looks great in Star Trek, but sucks in the real world. I want to be able to say, "computer, ${do something}", but with real voice assistants, I have to say "${brand 1}, use ${brand 2} to ${do something} on ${brand 3}".
