I think that when you put all of the interviews together (including the ones made prior to the ending), you get the sense that Kishimot wanted to make Sakura a proper heroine, but simply had no idea how to go about doing this. He tried to make her prettier and tried giving her new abilities, but nothing would stick and her popularity continued to be at issue. In one interview, he outright says that he will try to make her a proper heroine from now on. But no matter what he did, she just never fell into place. At the same, he's facing pressure from Studio Pierott (see one of the above interviews where he mentions said studio's desire for a NH movie). He's also watching youtube interviews from diehard NH supporters like Sawyer7 (who he specifically mentions as having watched). So finally, he says "screw it." Lo and behold, a one note side character becomes a heroine overnight and Sakura's arc spends the reminder of its time fading away into obscurity. A side character who I could literally and easily edit out of this 700 chapter manga in a smooth fashion if someone were willing to draw me 20-30 new pages of content and material.
Of course, I'm very much inclined to agree with our good friend, Riverkid and the following assessment:
And for me, I never really cared about "shipping" NS in the traditional sense. I simply looked at the character progression throughout much of the story and saw NS as the logical outcome of Sakura's character arc, especially considering the author has never specified a reason as to why she's in love with Sasuke. For much of the manga, her arc appeared to center around the themes of maturity and self-discovery and it appeared that Naruto's feelings for her was the vehicle for these themes to be explored. But alas, that never came to fruition. And not only did that never come to fruition, but so did a great deal of things in this series that simply leaves me scratching my head to this very day.
Where has Kishimoto said this? You know, about watching the YT channel of the NH fan?
Indeed, as I've stated right after I stepped on this site, I came here because it made sense to me, not for loving the couple, I realized their chemistry after reading NS supporters' arguments doe.