Yes, because he's kept being good for so long that he keeps getting to the latter stages of tournaments. It's the curse of being good at your job for too long. Like, a tennis player once they approach 30 is generally, historically nearing the end, they're certainly past their best.
I mean you could even backtrack that to include late 20s (Nadal was 28 when he fell into his slump, Djokovic was 29) but let's be generous and say 30 is the cut off point for anyone being considered anywhere close to their best.
He's been around for almost 10 years now in that post-30 zone. You can counter that with the comically vapid retort that Djokovic is now also in his 30s, but then of course the simple response is that ever since Djokovic moved into his 30s in this rivalry Federer has been 37+, and how many slams in the Open era have been won by dudes 37+?
1 out of 211.
The average age of slam winners in the Open era is 24-26, Djokovic turned 24 in May 2011, so you could say if you wanted (and I think it'd be pretty generous to do so) that prior to that point Federer had the advantage (Even though Novak at 23 would still be closer to the 24-26 age range than Federer was since, what, late 2008?) but let's again be generous and say Federer has the advantage in the head to head prior to May 2011. Their head to head at that point was 13-9 to Federer. Post Federer's 30th it is 18-9 to Djokovic. They've played 5 more times in that window (Interestingly enough if you discount the 5 meetings they've had since Novak hit 30, it's 14-8 to Djokovic, almost identical to the early rivalry's 13-9) so of course he has an advantage.
Of course the funny thing is the one time they met after Djokovic hit peak slam winning age and before Federer hit 30... How'd that go? And thus we come at last to the whole reason for this rambling mess of a post. A chance to post this GIF: