Just to scratch the surface, in 2004 Lleyton Hewitt, one of Federer's two main rivals and one who ended the year ranked 3 in the world, made the quarter finals at most 7 times in big events. Three of those times he advanced beyond the quarterfinals. In 2018, Marian Cilic, a second tier player, made it to the quarters of big events at least eight times, surpassing the quarterfinals three times. He ended the year ranked seven in the world. If 2014 is the year Djokovic's competition got weaker, then there are ample examples to indicate the competition he faced since then have been more reliable than what Federer faced in his early years of dominance. In my book, that consistency/reliability is the best indicator of overall ability.
Its one significant factor, but there are others. Ferrer for example was more consistent than Safin . No one with decent tennis knowledge would say Ferrer had more ability than Safin.
Getting back to 2004 Hewitt vs 2018 Cilic comparision :
Hewitt in 2004 made Hamburg SF, RG QF, Wim QF, won Cincy, USO F, Paris QF and the YEC F (Hewitt was also stopped by Fed in 4R of AO.)
He won 4 titles for the year. Went 68-18 for the year (79.1%)
Cilic in 2018 made AO F, MC QF, Rome SF, RG QF, Canada QF, Cincy SF, USO QF, Paris QF.
Won 1 title for the year. went 44-20 for the year (68.75%)
Hewitt made 3 finals - US Open, YEC and Cincy, actually winning Cincy.
as opposed to Cilic making only 1 final - AO.
Hewitt also won 4 titles to 1 for Cilic. had a much higher winning%.
But good job trying to equate those 2. Beyond delusional !
But Hewitt was your favorite player ? Ok.
yeah, if someone believes that, I have the Golden Gate Bridge to sell to him/her.