I can see why people are disappointed it was pretty much the same ending as the anime, but I did think the anime's ending was pretty good so I have no complaints ig.
Narratively we'd been building to Sato's death the moment she decided to kill her friend; that Shio seems to be going down a similar path is bleak, but i find it kind of cathartic too. Sometimes trauma just changes you, and frankly there was just no genuinely "good person" role model in Shio's life, so this makes sense. NGL I may have been hoping for the happy ending bc I love the characters, but at the same time I appreciate that the writer didn't chicken out and just give us an unrealistically happy end, choosing instead to give us a finale that was coherent with what came before.