The plot going nowhere isn't a problem. I'd be fine with even an episodic-style manga with disconnected chapters, save the only occasional story arc. The problem is that the characters themselves are going nowhere. Takamine has shown some progress - at least in the sense that she's trying more. But Shirota is getting even more boring, because he's become desensitized to Takamine. I can't even get a cheap laugh since he barely reacts to Takamine's perverted antics anymore.
What's the point? If MC is too comfortable with Takamine, why doesn't the author let him make a move? If not Takamine, why not at least use that chill factor with other characters? Make the payoff be that Shirota has so little thirst or is so unimpressed by other girls, as a result of constantly being surrounded by 10/10s, that it surprises his classmates. Anything would be acceptable, just not this overplayed "comedy" skit.