I think that what is off-putting is that she pretty much has a psychological disorder and instead the manga is presented as "ordinary life".
Komi-san, for example, is not presented as a "normal girl". The very first lines state that she has a communication disorder. Maybe if this was called "Niizuma-chan is afraid of sex" then all the jokes would make sense. But I went in expecting a cute normal newly-wed life with all the amazingly normal new experiences that come with marriage.
PS.:
@kamen9s I'm out of words. That is a crazy story.