It's an utsuge (depressing game), so condemning it for what it sets out to do is kinda silly. It's like blaming a comedy game for having good comedy and making you laugh.
Spoiler:
Also uhh, it's a shame you pretty much completely missed all the symbolism the game presented to you though.
Besides, all the other Innogrey game haves good ending. They are lacklustre though in my opinion, unlike KnS's true ending with its impact and emotions. But seeing you didn't felt that, and rather concentrate on stuff not crucial much, so I'd guess, you might like those games' endings more.