Definitively! Of the long list of issues I have with the anime, the ending is defo not one of them and that's something to be reasonably glad about. They didn't get the Game of Thrones treatment either, considering its length.

it’s one thing to have it as a fanfic and a headcanon if you want; and another to have it be flat-out canon in a previously happy series

This really needs to be quotable IMO. What is and isn't canon does temper the resulting fanfiction a lot.