It's just getting old, you win less. It isn't something that's solvable by a strategy change-if it were, guys wouldn't peak in their mid to late thirties.
This is pretty much it..... He's just gotten old. You win less because you have less consistency day to day. Plus it's harder to recover after a match and play the next day.
Yes he he can win, but it gets less and less likely.
I also think his chance to win on grass went when they replaced the old grass with rhy and use slower balls. They've made Wimbledon slower. It's more like clay now, so I'd say the US Open is his best shot, however slim.
7 matches playing at your best is a tough ask for someone his age.
Many will ask, well how does Serena do it?
I think Serena is just that much better than the field on the women's tour. No one can match her in speed or athleticism still, even though she is slower than where she started. The competition was closer to Federer than it was, or is to Serena.