Yeah, I agree that he unlocked a new level that year. Hard to say, though, if he was at his clay best, or just reached a new plateau. Meaning, he was already great in 05-07 but somehow got even better in 08. But was his 08 clay level really better than 10 and 13? Hard to say.
Yeah, that's silly (the "haters"). You can kinda fluke one Slam title, but not two - and more so, not five Wimbledon finals. I know titles are the thing, but in terms of level of play, I sometimes like to look at finals because reaching a final means you beat six other guys; winning the final means you just added one more guy to the list, and single matches can vary widely in terms of how well the two are playing at a time. The point being, Rafa reached five Wimbledon finals, which you can't fluke into - which is more than Andy Murray and the same as McEnroe whose grass pedigree no one denies.
Roger was the least adaptable of the Big Three which I think was partially due to his unsurpassed dominance in 2004-07. In 2008 he dropped a solid level against everyone and a still-improving Rafa surpassed him. When Roger returned to #1 in 2009, maybe he thought he could build on that and return to 04-07 levels, or at least stay even with Rafa. So for a few years, he didn't change anything, but things become more problematic when Novak went supernova in 2011. If memory serves, he only really started trying to change his game in 2013, his worst year in over a decade. By the time Roger had recalibrated a bit in 2014, he barely played Rafa (just once in Rafa's two bad years) until 2017.
The point being, it isn't that weird when you look at the timeline more closely. As a Roger fan, I wish he had applied his 2017 approach earlier, but looking closely at the timeline, I can see why he didn't.
As for why it worked in 2017, certainly Rafa wasn't the same guy he'd been in 08-14. But neither was Roger, and there was no real sign he tried to change things up before then. Meaning, it wasn't like he had tried to shift things vs. Rafa in, say, 2010 and it didn't work, but it finally worked in 2017. He must have had some ah-ha moment and, coupled with his refreshed body after the break in late 2016, he dominated Rafa for a bit.