I'm not critical person, but I admit there is something wrong. As one of light reading, Kuzumi certainly has flaws in it.
Even Horimiya, Nozaki and Tanaka still much better in their theme.
The author must do something about Kuzumi characteristic. He is simple, expressionless, but doesn't really stand out.
The one who work things out is his friend, and the one who struggle and develop the most is other character.
Kuzumi? Listening to music, whistling, feeding birds. It might be better to give Kuzumi's perspective to get to know his character better, how he feels, how he thinks.
As per now, it looks like it's coming to an end, but maybe no. If the writer wants to turn around then it's time. Or you could say the story is just about to start? In the near future, after they're going out, Kuzumi will get a lot of focus, he has to fix it.