I feel like maybe readers weren't satisfied with the ending because of the constant anticipation of something awful happening but in the end, things got to a marginally 'doing okay, tentatively happy' place and with all the build up, that may have been a bit of a let down/felt like not much of a payoff.
I'm okay with it, since really that's pretty much how life goes. And I'm firmly rooted in the 'that could've gone much worse' faction.
This kinda gives off the same vibes as Yoake no Uta.
They both have fantastic art, awesome characters, and a similar 'sacrificial lamb for the good of the people' thing going on.