The other couples are fine, though. What little of their lives together have been shown, it's pretty normal. This couple isn't. They're the weird ones. That's the point, the joke. It's not treated as how "normal couples" act. Niizuma's nature, being astonishingly sheltered, having no real experience in much of anything, extremely childish and easily embarrassed, that's the joke for the most part. The point. Someone this weird and abnormal attempting to live a married life.
The abnormality of that is acknowledged in pretty much every chapter, as that's where all the set up for the simple comedy comes from. The neighbors just casually suggested dumb things like naked apron or giving her erotic novels, and Niizuma just freaking out at that. She can't even properly buy potatoes and falls asleep while watching movies like a kid. She likes getting her head pat, for God's sake. Her childishness is as obvious as it gets. Much of it is established in the first chapter, where she was distracted by what might as well be toys, and it's stayed consistent to this chapter, where she was playing in a park like a kid, having fun on swings.
She's a childish, abnormally sheltered girl, which is juxtaposed with her trying to be a married adult. That's the whole premise. I know I'm defending it a bit too hard, but to see all of this, and assume the author is some incel that's lost his mind and thinks this is the norm, just seems like a pretty big leap in logic to me.