BECAUUUUUUUUUSE It's is a lose lose situation that starts and ends with one simple question, Why does "The Last" Exist? And they are shooting them selves in the foot either way.
Naruto is not a romance manga- then why was "The Last" a ROMANCE MOVIE to make NaruHina believable? Why is Naruto not a romance manga but they needed to make the the very first canon movie to the manga itself a "matchmaker fic"? Why wasn't this movie focusing on another theme that is not romance then If Naruto was "never about romance"?
Naruto IS a romance manga? then why was The Last needed to justify Naruto Hinata's love for each other? Why was Hinata not given any romantic scenes with Naruto yet so much effort was spent to make Sakura a "false lead girlfriend" all the way til the end? Again it is Not DIFFICULT to draw Naruto asking Hinata on a date, or even going out of his way to be with her regularly, now is it?
Is the Last a Necessity for an underdeveloped shipping or an unnecessary retcon and waste of time since Hinata was always the Intended "Mrs. Uzumaki"? The Hinata hierophants don't want to answer because they don't want to defile their religion
Epic post 
It's pretty much how you say, the Last was made SPECIFICALLY to make up for poor development in the source material, the motives of which are clear given that it was released MONTHS after the ending. They KNEW there would be questions (Kishimoto's interviews prove that).
They would have been better off if they waited a few years, maybe release it as an anniversary gift to the fans. Problem is, for that to work, NH had to work in the manga to begin with in order to make it unnecessary, but in the position they are now, it IS.
I saw a post on Deviant Art a while back with one person trying to defend the ending by comparing it to DragonBall, citing the episode where Goku and Chi-Chi after the Budokai go on an adventure to retrieve a fan before getting married. A few problems:
1) That episode in DragonBall isn't canon. The Last is.
2) Goku already agreed to marry Chi-Chi in the canon material. No one got squat in Naruto. No closure for NS, no crystal clear bridge for NH, and NO EXCUSE for SS
3) DragonBall NEVER had a pairing controversy. Toriyama just put two people together and never asked his fans to care about the development or find any deeper meaning with his pairings. Given that Kishimoto had to explain himself five times at this point, I think it's safe to say he's BEGGING us to buy into this.
4) Kishimoto already said that he only loved DragonBall until a certain point (namely the Frieza saga), so stop comparing Naruto to DragonBall. Just because one inspired the other does not excuse the mistakes made.
If we were going to have underdeveloped romance, I'd rather have everyone be as asexual as possible throughout the story. At least then we wouldn't feel like we were supposed to care one way or another with the endgame.