For some reason, Rublev kind of reminds me of Berdych. Booming power, somewhat one-dimensional game (and I think Berdych had more dimensions). A guy who seems to always be around, but not win Slams.
For whatever reason, Berdych went deeper in Slams: he reached a final and 6 other semifinals, along with 10 other quarterfinals. Rublev, on the other hand, has never made it past the quarterfinals (9 times, including 5 out of the last 6 Slams he's played in). Not sure what is, but he can't get past that QF hump...yet.
One thing to note is that Rublev just turned 26, so 2023 was basically his age 25 season. Berdych turned 26 in late 2011, so that would be the equivalent, age-wise. At that point, Berdych had one F, 1 SF, and 2 QF...meaning only 4 times to the QF vs. Rublev's 9 times. But Berdych didn't really reach his peak form until around the same age as Rublev over the last year or two, and was solidly good into his early 30s with lots of SF chances after Rublev's current age. I expect that he'll have some SF appearances, and maybe a Final or two. But he's definitely pretty much the definition of "second tier" player at this point - ala Berdych and Tsonga.