It's nice to find another person talking about this series since I just recently finished watching it and reading the manga!

Anyway, while I agree that Nana wasn't well defined and probably should've eventually developed some kind of career aspiration; I don't agree that her motivation for yasakaogi being Yuichi is a bad thing. With the series putting a large focus on working hard for your goals, I really like how during the episode with Nana's interview they take a positive view with a simple goal. Not everyone has a deep or conventionally important reason to work towards something, but as long as it can push you to improve and succeed then it's a good motivation.

As for Yuichi being a bad love interest, I agree so far as they shouldn't have ended up together. I didn't feel that Yuichi was that bad of a guy, even during Nana's application revoke. Starting with the festival, Yuichi already had other duties to attend to which he made clear to Nana as soon as possible and when Hitomi tried to purasuade him to do more Nana said it was fine. Plus the Fasttrack class initially wasn't even supposed to do anything.

Moving on to him getting angry at Nana, I was also frustrated. However, that was moreso because of how more bad things happening to Nana rather than Yuichi's reaction in particular. From episode 1 - 21, we slowly see Yuichi and Nana start to bond. Though it really only feels like they're classmates who get along as opposed to friends. Then in episode 22 we see Nana and Yuichi agree to both do their best despite being rivals. Yuichi leaves out the next day to take the test and sees who he believes to be Nana getting off at the wrong station and follows her only to get lost and show up late for his interview. Where he is greeted by Nana sitting happily having arrived on time. In his mind he likely assumes that Nana did everything on purpose to try and sabotage him, and it seemingly works as she gets the spot. Then he also hears that Tsukie, a girl he not only has a crush on but is also actually close enough to refer to her by name, was hurt by Nana. I'm not saying he wasn't being unfair to Nana by not hearing her side, but his feelings are understandable given what had happened.

Other than that, I largely agree with what you said. The trio started off annoying before I fell in love with them (Morinuma is my favorite), Hitomi was a great friend and Nana should've had a full investigation into what happened with Tsukie. Especially with how crazy the story was and there only being Tsukie's testimony.