One thing to consider about younger guys like Fils is that even when it becomes clear that they aren't future super-elites, they could still develop into more garden variety elites. Think of Dominic Thiem, who didn't finish in the top 20 until 2015, which was the year he turned 22. Thiem finished #8 in 2016, #5 in 2017, #8 in 2018, then #4 in 2019, winning his first big title at age 25. He won his only Slam the next year, just before his 27th birthday - and seemed to have arrive as a true elite, finishing #3. Of course things didn't go well after that, but it was due to injury, not decline.
Thiem's rise was a bit more steady than Wawrinka's, but like Stan he didn't reach his best form until after 25. Meaning, it wasn't only Stan that peaked late in the modern era, but Thiem also found his best form at age 26-27. Or we have Andrey Rublev winning his first big title in 2023 at age 25 (Rublev finished #23 in 2019, the year he turned 22 - was on a similar arc as Thiem).
Now Fils finished in the top 20 last year at age 20 - so he's two years ahead of the "Thiem-Rublev timeline." Thiem, at age 22, wouldn't reach his best form for another 4-5 years; we don't know if Rublev has peaked, but it is noteworthy that he didn't win big titles until after he turned 25.
So my point with Fils and other young guys is that even if it becomes clear they won't be in the same category as Sincaraz (and very few players ever are), there's still room for further development. In today's game, players seem to continue developing up until their mid-20s.
Even someone like Felix, who turns 25 later this year, could re-find the #6 form he had in 2022 and maybe even get a bit better, winning a big title or three in second half of this 20s. Or Jack Draper, who I remember someone mentioning way back when he was 15 or 16 years old then never seemed to develop for years, but then popped onto the radar in 2022 when he went from #265 in 2021 to #42 in 2022. He fell to #61 in an injury-plagued 2023, but rose to #14 in 2024, the year he turned 23.
We all like to focus on the greats (or potential greats), and write off players when it becomes clear that they won't become that. So we get excited about Fonzie, and have hopes for Tien and Mensik. But I also really enjoy watching how the next tier or two of players develop, because they often have intriguing arcs. So while I am just as excited as anyone to see how many Slam trophies Jannik, Carlos, and Joao end up with, I'm equally intrigued about who else might win Slam titles and other big titles to "fill in the cracks."
Just a bit of rumination, looking at Fils' loss today and seeming, perhaps inevitable, stumbling towards the "bucket of disappointments." He isn't a disappointment, just settling more into an elite or near elite group of players who aren't as good as the very best, but are still quite good - and interesting in their own right. And best of all, there is a sense that this group will hold a greater share of big titles in the coming years than the comparable group of the Big Four era.