There's all this misery, and nothing was done with it.
[SPOILERS BELOW]
Tragedy is a legitimate genre, is it not?
And the last part gives some redemption, does it not?
And each character is given a full arc, are they not?
Feeling frustrated or depressed is one way to react to a sad story, but there's another. Despite our evolutionary desire to tie a bow on everything, it can be beneficial to our well-being to accept that sadness is a fundamental part of the human condition. This is because well-being can be defined as how closely reality meets our expections.
Or, if we want to find a moral to these stories, it is perhaps not to allow ourselves to become so emotionally attached to something that it can undermine our very being. Logically, neither failing to gain something we expected to gain, nor losing something we didn't expect to lose, should leave us worse off than we were before we obtained the desire to have these things in the first place. Therefore, the suffering comes from an immaturity of the soul, or more scientifically, undisciplined thoughts, rather than an external source.