Difference is Fed often outplays Nadal, dictating the point but then Rafa will make an unbelievable get and stab his racket at the ball and it just sneaks past Federer who has shown more "calculated" skill.
As for "never too old" Nadal just got worse. Once his physical and age advantage was gone Fed's far superior tennis ability is now shining through. Shame Rafa ducked him for the whole person between 2014 AO and Basel 2015.
As for Fed ducking clay, he's simply returning the favour like when Rafa ducked Fed at every HC slam 04-08, every Wimbledon between 2012-2016, most HC tournaments post Wimbledon etc.
To be fair to Nadal, Roger has had a few losses, during the early part of this decade, where he wasn't able to reach the later rounds of a slam and thus avoided a potential beat-down from Rafa.
In 2010, he lost to Djokovic at the US open in five sets (despite holding two match points.)
Had Federer won the match he would have faced Nadal in the finals. Given their form, at the time, Nadal would have almost certainly won the match.
Ironically, the same exact thing happened in 2011. Where Roger had Novak down two sets to love and still wasn't able to finish him off. I believe he also had two match points in this match, although I could be mistaken.
In 2013, Roger was within one match of playing Nadal, in the quarter-finals of the US Open.
His fourth round opponent, Tommy Robredo, beat Roger in straight sets despite having had a 0-10 record against him going in.
There are probably others, as well, but the point that I'm trying to make is that it wasn't due to a lack of hard court proficiency that Rafael Nadal wasn't able to play Roger Federer more often.
That might have been the case in their early years (2007 and before) since his results could be quite erratic back then.
However, he was more than capable of holding his own against Roger on the faster surfaces, once he had reached his prime years.
Not trying to pick on Roger with this comment but I want to be fair to both players.
Nadal is a very credible hard court player. He has to be or he would never have won the US Open twice.
The same number of times that Agassi, Rafter, and Edberg triumphed there.
He's still in elite company with the results that he's had on hard courts.
But his proficiency on clay dwarfs what he's done on the other surfaces to such an extreme level that's he's often criticized for being overly dominant on one surface.