Well, that's funny because I'm agreeing with you (I'm not >>10157964
. That's not a good storytelling and I find the ending rather lame. After episodes of BAAAAAW (the one where one character dies by the hand of the evil guy, and the one when she discovers the dimension of Karasu), we got the easy ending.
But it makes sense, and it's not illogical as you may have stated before. IT's precisely because of the whole "there is mutiple futurs" that there is still hope in the future, granted that there is a dimension where "everyone is happy", and thus this end.
On the opposite, the evil guy was only living in the past, his clarity of mind shadowed by the death of his Haruka. The opposition is quite clear here.
So there is no problem with the rules of Noein dimensions.