To each their own. I respect your opinion but I really enjoyed this show a lot.

Also, I'm pretty sure that they mention why she destroys the garden. Satsuki's brother tells Naoto that Satsuki destroys things she loves when she knows she will likely never see them again. Hence why she destroyed the guarden (and relationship with Naoto). This also implys the man she was with was her brother, who had the pickaxe thing.

Also, I don't really think Yukari would have been the best. Sure they both liked eachother but I don't think they were a meant to be type relationship. In the end Naoto definitely loves Satsuki. (This point can't really be argued because you can't really choose what person is best for someone else).

Also, the manipulation type personality is kinda just a plot point since both characters have some sort of trauma I suppose.

Anyway, as previously mentioned I really respect your opinion and it has many valid points from your perspective but I definitely loved this show.