Sorry it was late when I wrote that. Let me rephrase this. Hinata wasn't as overly popular as SP and SJ thought she was. But that is what they perceived because of her vocal fanatical fan base. Was Hinata popular enough for her to completely dominate the flow of the ending and rewrite the entire manga? No of course not. But SP and SJ thought she was based on both vocal fans reactions and desires in both kishi's and SP's staff.
Was hinata popular yes. But why was she popular? Well people already answered that I assume. But why wasn't she hated as Sakura but then suddenly got a lot of flack after the last? Simple her popularity was that of a minor/darkhorse character. People like her concept and then filled out her personality of what they wanted her to be, and that lead to a lot of people becoming fanatically devoted to her. The people that didn't like just ignored her because she wasn't that important to the plot. And if they did hate something about her it was her fanbase. But once the ending and the last happened they tried to move her to heroine status and she flopped. Because now people had to look at her and all her flaws. Which why they started to hide her after the Last and don't overly use her as much as they use to.
Yup, putting her into heroine seat means putting her into a spotlight where everyone can see her and every details of her character development, flaws, and characteristic will be revealed. In the manga she was not appear much except at those 2 moment that give her extreme boost of popularity, the suicide confession at pein arc and the hand holding scene at the war arc. So its natural that people will like her over Sakura and think that she is the one that should be heroine. They put her in the heroine seat in The Last, but after many of NH fans sees what she truly is in that movie, she care about her love and obsession for Naruto over her own kidnap little sister, any "SANE" NH or Hinata fans starting to doubt their own believe, is this girl is really fit to be the heroine??? is this girl is any better than Sakura??
So yeah i agree like Bail said, now they starting to hide her, and focus more on the SNS or Sasuke and Naruto yaoi relationship. But who knows, maybe i was wrong and maybe in the Boruto manga she will appear a lot.