I don't think you have really read up on the history of tennis. In the past it wasn't as uncommon as it is today to have 30 years go far deep into the tournament. For example, Jimmy Connors came back from 2 sets to love against Aaron Krickstein at age 39 to reach the semifinals or Rod Laver winning 45 titles after age 30 and at one point was even number 4 in the world at age 36. The few "old man runs" I can think of was Jonas Bjorkman when he had a terribly easy draw at Wimbledon 2006 while he was aged at like 31 or 32 he reached the semis and also Pete Sampras's USO win at age 32. Other than that, it has been quite the young man's sport.
He was in fact 34.
Quite amazing when you come to think about it.
We're definitely writing alot of players off to early these days.
I mean a player like Murray can for sure do as Bjorkman did and reach SF in Wimby the year 2021.
Fed can have 5 years left in the top 5/top 10.
The top players are so well trained these days. Barring injuries it's only lack of motivation and drive (read: borg) that is really stopping them from success post 30 years.