I'll get the ball rolling...
Let's start out with a really controversial one:
Injury excuses ARE valid.
Yeah, I know. They're irritating. Nobody wants to hear them, especially when they seemingly discredit your favorite player or are meant to absolve someone you dislike. Additionally, as a disclaimer, you are absolutely entitled to not want to hear it. They're boring, and often times unsubstantiated. They also can be thrown around wildly and liberally.
Excuse makers are annoying, no doubt. Many have absolutely mastered the art, whether by directly mentioning them (Nadal), or as Novak masterfully displayed last night, by indirectly alluding to them (ie...now is not the time to talk about physical issues, I don't want to take anything away from *insert winner name here*, etc...).
But yes, they are valid. And yes, they can greatly affect results. I fully understand the very pragmatic "if you're injured, don't play. If you play, you're not injured" and that's a motto meant to put an end to a potential rabbit hole, which again, I understand. It is however, crazy to take it literally.
Having listened to so many podcasts/interviews from retired players, you'd be surprised by how injuries are perceived by players. These guys are in the locker room and see everything. They know when players are hurt or playing through injury, especially significant ones. Hearing Casper Ruud himself discuss Nadal being on crutches after his defeat to Rafa at the French Open in 2022 was eye opening, as well as other players' take on the subject. While the partisan crowd on forums finds this tedious, quite understandably, I've noticed that players see it differently, most likely due to being so close to the action AND being professionals who are hampered by injuries themselves.
I realize that as a Nadal fan, this is quite convenient for me to say. And I've always been of the opinion that Nadal fans around these parts can be majorly annoying (Hi Anti-Pusher, in case you're reading this), or in some cases, grade A idiots (Hi MikeOne). But the way "Nadal's injuries are a product of his playing style" was just a go-to discussion ender thrown around with stunning ignorance and complete lack of credible knowledge to end any potential discussion on the subject, always struck me as ridiculous. There is zero evidence to that, especially when his body broke down with a wide variety of injuries, and not just some chronic tendinitis. It's also silly to say this with that level of irrational confidence when other top tennis players were also covering so much ground, sliding all over the place on hards (now more than ever), retrieving everything, etc...
Rafael Nadal has missed about 17 Majors due to injuries (by my count). Among those, at least 10 have come sandwiched between his first and final grand slam wins. So while I fully get why this is a slippery slope that could lead to some never-ending debates, it is equally ludicrous to deny that he could have, and yes, would have won more if he played even half of those. Rafa roughly won 1 out of 3 majors he played during that span. He almost definitely would have won more had it not been for injuries, and that's not counting the toll of constant rehabs, getting back into shape, playing himself back into form, etc...
Listening to Nadal talk about how his grass game was affected by his knees between 2012 and 2017, and how much better he was able to play on grass after that in that amazing interview with Roddick (I urge you to listen to it as his breakdown of his matchups with Roger and Novak alone are worth it) puts it in perspective. Incidentally, I've said that over the years around here and got into endless debates with everyone about it.