I'm thinking we're starting to see the decline of "Next Gen" - Medvedev, Fritz, Tsitsipas, and Rublev are all having off years, and for at least three of them (not Fritz) the "wobble" goes back to last year.
I'm not saying that these guys can't rebound, but they're all in that late 20s window when a lot of players have a bit of a lull (Medvedev just turned 29, Rublev and Fritz turn 28 late in the year, Tsitsipas 27). Some just keep falling, though a lot have an "Indian Summer" of some kind, even for several years.
Poor Next Gen. Second generation in a row with no truly great players. The following gen has two greats (Sinner, Alcaraz), and a few top 10 types (Draper, Rune, maybe Shelton and Musetti); and the post-Alcaraz gen is also starting show some promise (Fils, Mensik, Fonseca).