Whatever the reasons are, Naruto makes us feels so much more about the whole pairings when in the beginning, most pairing fans just started as simple fans of the serie, like most of serie we like I guess.
Naruto was overly sentimental (even by shonen standards) and also strangely fixated on romantic themes even aside from the MC (with Obito and Jiraiya etc) so it just tends to sit badly with people that they got it wrong.
It's like if you lived your whole life really wanting to own a fast car and you never had the money, then you finally win the lottery but the car you buy is a 2001 Prius with 300,000 miles on it. It defies expectations in a bad way.