Maybe I’m just dumb, but other than the music evoking it - I really didn’t see Rogue One doing the classic gee-whizz space opera? They were kind of going from tragedy to tragedy, under the orders of a militarized intelligence op. Interspersed with drama more than any of the characters having some sort of clever fun. And they all die in the end.
I think the whole “grimdark tone” discussion is off-base of what I was actually saying about Rogue One’s internal logic though. ESB could be dark, ROTS could be dark, The Clone Wars could be dark. Rogue One is moving in a different space than just gesturing towards unpleasantness in the ways those do. I’m not denying the tonal dissonances in Rogue One, but the proto-Andor DNA can’t easily be washed out because K2 has some one liners (I’m assuming?).