It's a fact. He might not have been able to hang with the current top 4 post surgery, but he's still comfortably a better player than anyone else. He's also 5-5 in his last 10 matches against said top 4 so the signs are that the gap is closing, not increasing.
Surgery/injuries have affected his relative standing in the game compared to the current top 4, but that's all. He's still better than everyone else. This has been the case ever since his return.
So, your ONLY real argument is that he is doing well against top 4, since David is ahead of him in every other aspect of the game.
And yet, it is preposterous to say that Fed cannot be goat because of his h2h with Nadal.
Man, this exclude-the-rest-of-the-field-when-it-suits-me game is sure darn difficult to grasp.