It definitely doesn't excuse the bad writing, which is one thing people somewhat keeps dismissing. After reading/watching other series, this series truly is a mess. You may say, "But you're comparing to others. That's not fair." Even so, it's still a mess. I never seen a series that has somewhat obvious pair whether it happens or not, only to go completely off the radar. Not even Bleach was this bad.
Bleach as much as one might disagree did set up the end pairings long before hand. Orihime always had a crush on Ichigo, and was notice by all their companions(who all seemed to support her attempt to gain Ichigo's attention). Renji as much as some of you might disagree was heavily implied to have feeling for Rukia since at least his second fight with Ichigo.
It definitely backfired. I don't think he was expecting the amount of negativity he got from the bait-and-switch ending. And of course, it didn't have to be that way. He could have fleshed out his characters, made believable romantic storylines and most importantly not sacrificed Sakura and her happiness at the altar of Sasuke. Honestly, I think if Kishi had done right by Sakura and given her a better ending with a mutually loving relationship with SS, people would have been...well, not exactly happier, but at least satisfied.
You're exactly right: the fact that Kishimoto is still focusing on this single issue of shipping, loooong after the ending, shows that it's still a problem. That he knows he pulled one over on his fans, and he's still having to justify it.
Yes, I remember it being mentioned that Sakura alone was the only other person in all the movies, outside of Naruto and Sasuke. It was always Sakura. You can't just erase years of development and storylines by saying, 'oh that? i didn't really mean that! when you saw Sakura you should have been thinking of hinata instead!'
Right - I think it has to do with pushing Boruto and the merchandise. I have to wonder, if SJ interviewed him and there wasn't a Naruto spin off going on, what would Kishimoto say instead? Would he still be pushing NH? Or would he relent and say that things could have gone different ways, with NS and SK like after "The True End." (Or would he tell the truth, that he really didn't care about any of the female characters at all??)
Do it. Do it. Do it.
Exactly - the fact that he parallels these relationships all over the place is a dead giveaway of what Kishimoto had planned. NOWHERE is NH paralleled. It's always a triangle.
They thought that the international fanbase; which was the main appeal of Naruto to SJ was a nH supporting majority. So they were willing to abandon all their other fans for it.
The reason why kishimoto can't stop talking about it is because the decision to support the retcon is still haunting him both in his career, his personal life, and mentally. His career and his reputation was destroyed by the decision to go through with it, and now he stuck being the editor to it sequel. His wife is upset (she may have forgiven him at this point but "the decision" probably still hurts her) about him not pairing up the characters that represented the two of them. The kids since kishimoto is never home from what I understand sided with mommy and do not respect him. His brother has been able to do another manga in the time he been stuck keeping an eye on Boruto. Father died before the ending, so he has to wonder how he disappointed his father would be if he was still alive. Mentally look at the last few sentences his professional and personal life was ruined by his capitulation.
What is more humiliating being proven wrong about some of your story's romantic pairings or being right but was convinced you were wrong so you change the pairings at the end thinking that what your fans wanted only to discover you were right at the beginning and your capitulation destroyed everything?
Sakura was in every movie from what I can recall other then Naruto no other character can claim that.
Look at the interviews after they realized the last was a failure, but before the Boruto manga started for your answer on how he reacts. He clearly resents the pairings nH/SS for destroying his life, and can't stop talking kitten about them or the people who convinced him to go through with them (indirectly in the latter case.)
Yes! I passed over that, but you're exactly right! Well put, Bail.
So is there a trope name for when a hero gets dumped at the end of the series? Or when the anti-hero ends up with undeserved swag while the hero just gets the satisfaction of doing everything for the greater good? Or when the hero's stated goals remain unfulfilled?
I looked at tvtropes, but I'm just having a hard time even nailing down what exactly I'm looking for. "Author gave up on hero in the end??" 
Edit: Found "Decoy Protagonist," but everything listed underneath it seems to be standard twists to keep the plot moving. What Kishimoto did, of undoing the hero's goals and shuffling the pairing, doesn't seem to fit into the tropes. Maybe we should create one called "Author Makes a Quick Exit!"
Naruto is Sasuke's morality chain not his rival. There really isn't anyone that gives Sasuke any challenge by the end. The Uchiha are no longer the main villains. So all that's left is Sasuke redemption journey. So the only thing that is challenging him in any way and striving him to do better is his past. Hinata was given the ending, and since Sakura is no longer the heroine in the eyes of the creative team she get's the title by default. Orochimaru is the one in the novel to tell Sasuke he should be the guy who works in the shadow to protect the village. So the way Sasuke acts is because of Orochimaru's mentoring not Kakashi's.
There isn't really any one thing to describe what happened with the ending. One would have to make a list of tropes.
Think back to all the non-manga ads, posters, sales promotionals, etc. It was never Hinata. It was always either Naruto and Sakura being happy, Naruto and Sasuke fighting or it was Team 7. Cardboard cut out for for a blood drive? Naruto and Sakura. Promotional wrap of a train car? Naruto and Sakura. Figurines, plushies, posters and jewelry? All yes for each member of Team 7. Not so much for Hinata.
Someone compiled NS moments from the manga, it would be interesting to compare how much Team 7 (and specifically Naruto and Sakura side-by-side) images, ads and toys were put out there vs. Hinata and Naruto together. Or even Hinata standing out from a general group pic.
Kishimoto can "say" all he wants about how important Hinata is. But he can't rewrite the fact that up until the end of the war arc, no one gave a crap about Hinata. Including him.
Remember how after the tsunami a few years back the way they told people not to give up hope was a NS ova?
Apparently there was a hinata clock that alarm was Nana Mizuki singing her song from the last. From what I understand it did not sell well. The only thing hinata sell really is love pillows.