Intensity, especially in promos. Back in the 80s and early 90s, when wrestlers stared into the camera and told you they were gonna fukk you up, they looked like they meant it. Legit mark-out moments actually happened back then.
Today, poorly written comedy is incorporated into almost every segment. It is impossible to take anyone seriously. Everyone always knew it wasn't a sport, but today they don't even try to pretend it's serious.
This of course is all related to kayfabe being gone and the Internet exposing everything that goes on behind the scenes. It had to happen, and of course it gives us a lot more to talk about, but the end result of all of us being in on the joke is that none of us get lost in the moment, even for a second.