30's were ancient from approximately the mid '70s to the mid 2000's.
Before and after, players still primed/peaked in their early to late 20's but the difference wasn't quite as vast, assuming passable health. Equipment/tour stability (latter is more of a factor from '07-present) made it harder for younger players to break through/exploit their peers' comparative late-life adjustments to new technology like graphite and poly.
Where there's more variety and equipment shake-ups, there is less long-term dominance. This becomes increasingly clearer the closer one looks. It was only during that roughly 30 year span that tennis was a DISTINCTLY young man's sport (almost all sports are "young man sports", but I'm relativizing here).
The period you're referencing was one of the most longevous in tennis history for top players, fwiw. Rosewall, Laver and Gonzales among others all enjoyed very good/great longevity.
While I agree with some of your points, and yes, they are fair and valid, here's the thing.
We keep hearing here over and over that physical peak is in your 20s, that testosterone and all the other good things peak in your 20s and then decline. You are addressing the wear and tear, yes, but biology is biology, and Laver, according to the Djokovic detractors was past his athlete peak by that age, and while the game might not have been as physical, it is offset by the fact they also didn't have the advancements in modern science and nutrition and recovery. And lets not forget, tennis wasn't as global as it is now.
If they are all playing into their 30s, then Laver was winning his CYGS against other players who were also passed their physical peaks. Biology doesn't change, right? Where are the physical peak players we constantly hear Djokovic haters bringing up, when it came to Laver winning a CYGS?
The reason why i bring this up is, and which has now been admitted by Djokovic haters is simple....No one cares enough about Laver, it is too far in the past, and these people were mostly invested in the slam race, so Djokovic winning is what bothers, not what Laver did nearly 60 years ago, it also shows that the slam race was the actual metric that many were using to determine who would be the GOAT. You've been here long enough to see how each fanbase gloated about the numbers, I don't need to say it, you know this and have rightfully pointed it out yourself in the past.
And if Laver can do it with the game not being as physical, why cannot modern medicine and science and nutrition, the most elite training and recovering systems that have ever been seen by mankind, not show a different path to achieving elite level success, especially if you are genetically gifted? I mean, how many people are able to show the flexibility and court coverage Djokovic still shows? Dude can run into splits and still hit massive passing shots past top players.
Has Djokovic aged, yes, of course he has. But how is he offsetting it, so he can peak for big events? By playing less, keeping his body fresher, optimizing what he has for short periods. But anything he wins is simply down to everyone being bad.