If I could bring one thing back it would be just plain old _websites_, when people would make a place on the internet dedicated to some topic that was organized in a way _other than_ chronological order, and just became a great resource where important information was always easy to surface.
Here's a great example that will probably trigger some nostalgia for anyone who grew up on the late 90s internet:
I was just looking for good academic websites in my field, and I found that for the most part, they're gone. They still exist, especially Google sites. It's just that they're purely for promotion. Almost entirely things an employer would look for. 20 years ago, you'd have academics putting material on their websites to provide information to others.
Apparently, they've stopped posting it. I'm referring to things like advice, introduction to the field, a bibliography of the important papers in the field, why they love their research topic, and that sort of thing.
Here's a great example that will probably trigger some nostalgia for anyone who grew up on the late 90s internet:
http://www.petesqbsite.com/