One thing that might be a factor--even explain--Felix's "lack of fire" (to quote Kieran) is that he has a chronic heart condition. I believe he had surgery to correct it some years back, but I do wonder if that plays a part.
I see a guy with a similar display of raw talent and range of skills as Sinner and Alcaraz, but lacking that "it" factor (contrast him to Holger Rune, who is more rough but definitely has the "it" factor). I'm not sure what it would take to get him to that next level, but as I wrote elsewhere, he's kind of missed his window for "the path to greatness," at least in terms of historical Elo ratings. Now just as Stan set new precedents for multi-Slam winners and "near greats," presumably someone comes along and doesn't fully blossom until their mid-20s and ends up becoming an all-time grat. But even Ivan Lendl, who didn't win his first Slam until age 24, made a huge jump before--and was an elite player by--his 21st birthday (then continued from there).
Or consider that, along the lines of my study in another thread, every all-time great (6+ Slam winners, plus Murray) had surpassed the 2200 Elo threshold before their 22nd birthday...Felix's peak is still at 2140 and he's 22, going to be 23 in August.
So again, who knows, maybe he sets new precedents like Stan did, and makes a big jump over the next year or two, but right now he's more on a path that sees him becoming somewhere between Gasquet/Dimitrov and Medvedev/Thiem. No shame in that, but not quite at the level of all-time greats.