Then you should also have been skeptical when it took an inspired Djokovic at his absolute peak to deny him in 3 Slam finals and a semi-final between 2014-16, when he was a sprightly 33-34 years old...
People can have their suspicions, but the simpler explanation is the obvious one. Federer is the master of giving himself opportunities. It's no coincidence that the "Weak Opposition" talk has re-started after Wimbledon (after going silent when Djokovic had an incredibly dominant season in 2015, and Nadal to a lesser extent in 2013). I can accept that those two at their absolute peak probably beat him more often than not in Slam matches. But the question is, did Federer ever go away? He has always absorbed the tough losses, maintained his level and kept coming back. So when Djokovic had a drop-off (Murray as well, though Murray hasn't really been a problem for Federer since 2014) this year, guess who was there to capitalize. No one is better at being there at the business end of Majors year in, year out than Federer, so take away his biggest obstacles, and he's back in the winners' circle. 2013 and 2016 were the only "poor" seasons he's had, and those can be explained by injury, and adjusting to a new racquet.