yes, fair, Federer does illustrate that if you have the skill, then you can still be competitive despite declining athleticism. On the flip side, I think Meat is also right that it shows that once you cannot hold that elite level of athleticism, then that becomes a limit on how dominant you can be.
Setting Federer aside, though, I'd be very baffled if you honestly disagree that tennis has become much more athletically demanding and physical across the decades. I reckon that's a pretty universally agreed-upon matter.
This isn't me arguing for BO3 at the slams by the way. I'd ultimately prefer it to stay BO5. But I think the pro BO5 side has a much stronger case if they can grant that some of the BO3 arguments hold some merit. It isn't that the BO3 crowd has *no* reasonable points; we should instead maintain that the upside of BO5 ultimately outweighs these points.