Sakura was always popular in Japan save for certain lulls because she wasn't doing anything. Western/US fans hated her and were convinced everyone one else must hate her. I think the big example they like to use was one of the last character polls while the manga was running and Sakura was #11 with Sai which they convinced themselves that means Sakura isn't even popular in Japan. When it was more, 'she was liked, they just liked another character more than her, often Naruto/Sasuke/Kakashi, but she was never hated.' While comparison Hinata fans often love her the most or love only her, so they always voted for her, she had a small but dedicated fanbase in Japan. Which is often why Hinata would rank high in polls while certain conditions are required for Sakura to though when those happens, she beats Hinata easily. This poll which is female characters so no Naruto/Sasuke/Kakashi, or that poll two years ago for 'which character would you like a one shot of' she got third behind Minato and Itachi. There were others over the years but I've forgotten the details of those.
Sakura in Japan. An interesting take on her archetype for the time. A tsundere that wasn't in love with the main character from the start and he had to win her affection; making the romance more interesting and worth investing into compared to most shounen romances. A heroine that had to join in the fight and be involved in combat during a time when shounen really didn't have their female characters fight. Even when that changed, she was still unique because she had a lot of uncertainty and doubt but still had the resolved to improve herself to help out the people she cared about. Something resonated with female readers and is hard to replicate even for modern shounen heroine.
Sakura in US. Filthy useless ugly slutty abusive friend-zoning whore who should die a thousand death!!!
Hinata in Japan. One of the most generic examples of her archetype ever made. Generally forgettable and uninvolved in the story till the very end and doesn't have much character. Though is great for fantasizing your perfect dream girl because you can make her anything because there aren't that many details that will contradict your fantasies.
Hinata in the US. Most perfect woman to have ever existed. The story should-no, is about her. It about her getting everything she wants. She deserves it. She is entitled to it. For being so perfect despite being the most abused and oppressed character to have ever been written. No one have ever suffered more than her and she never deserved it.
With those lines of thoughts in mind. Is it a surprise there is confusion between the Japan/Kishimoto and the American fanbase?
Sakura lowest point of her popularity was the ending because she backtracked to square zero of her character arc. It improved since because of the fact they refuse to use her in the sequel means she isn't tainted by the issues it has, because she is not involved, and her daughter is well behaved and well received compared to Hinata's spoiled brats.
I find it funny that the same things you say about Hinata, Naruhina, Sasusaku, and Sakura in the U.S. are extremely similar to what happened in my country, Brazil