Becker is just being a sour puss because Rafa has eclipsed his accomplishments and Djoker is on his way to do the same. Nobody here knows, whether you are a pro player has been or not, how Rafa or Djoker would have fared in the 70s, 80s, 90s.
Who's here to say how each one would have adapted to a specific era to dominate like they did. Everything here are mere speculations which are all dependent on our respective bias and allegiance because nobody here will ever know. Just My 2 cents.