Federer had 11/10 talent, but was not mentally strong
Federer had the same problem of Navratilova (when she was the best female player for most of the 80s)
she was so good that she won almost every match very easily, but the few times in a year a rival managed to play at a super high level and give her a tough match, she would probably lose that match.
Mental strength is almost like a muscle, and you don't train it if you never struggle and win most matches very easily.
Federer was also the best tennis player ever for youtube highlights, he did spectacular shots very regularly.
I think 2000s Federer was the best tennis player ever, but Novak is the greatest tennis player ever, and the best 35 years old athlete ever of all sports.
I have never seen as athlete age as good as Djokovik, the difference between 35 years old Djokovic and 23 years old Djokovic is very small.