To be fair, I found that the simple fact of his homeworld being gone was adequate grimdark for Superman. I actually greatly liked the story they did to explain how he is the only survivor of planet Krypton, but not the only Kryptonian. IE, all the others from the HW died, but some of those on colonies survived. Which eventually lead to this:
OK, technically that's Siobhan Smythe, and not a Kryptonian, but Supergirl's reaction was like that because she actually HAD met random Kryptonians.