When Seth Rollins won the WWE Championship at WrestleMania 31, he made history as the first man to hold the title born after WrestleMania I. Yes, age is theoretically only a number in pro wrestling and that number can be refreshed with creative, but Rollins' victory in particular was a small but significant turning point for how WWE's roster would shape up in the months and years to come.
Performers - particularly those that see WWE as the final destination in wrestling - were probably heavily influenced by that specific product at one time or another. Hulk Hogan worked for the McMahons before the AWA, even if it took the lure of the Son rather than the Father to get him back in 1983. Steve Austin got the wrestling bug going to watch World Class Championship Wrestling at the Dallas Sportatorium, but he considered WWE the be all and end all even at its lowest commercial ebb in 1995. John Cena's family memories are all of him going to the Boston Garden for WWF shows and holding up homemade titles. The Miz watched Raw every week with his frat mates, in case you haven't seen him mention it on ten separate documentaries.
This isn't just another call to "watch some older stuff sometimes, please" from a 35-year-old writer that often feels too old for WWE despite not being closer to its core demographic than most that buy the merch. It's a reality check for what the wrestlers of today saw when they first turned the show on in the early-2000s.