I've watched this two times already: first time with 17 and now with 20.
By this, i can say that this drama is really more 𝗺𝗮𝘁𝘂𝗿𝗲, since only now i could look at it with the right eyes.

First of all, Nabi is a typical person with 𝗮𝘁𝘁𝗮𝗰𝗵𝗺𝗲𝗻𝘁 𝗶𝘀𝘀𝘂𝗲𝘀 and some childish manners along with it. It's even concerning to see how she gets quickly obsessed and jealousy. But, at least she can recognize her own pathetic ways.
And Jaeon, the first impression we can get of him is a 𝘁𝘆𝗽𝗶𝗰𝗮𝗹 𝗽𝗹𝗮𝘆𝗲𝗿. The way he talks, how he moves, his gestures, it's all with the intent of seduction (and it can even get a bit cringe sometimes).

The first view that Nabi gets of him isn't much different from the stereotype, but it gets worse 𝗱𝘂𝗲 𝘁𝗼 𝘄𝗵𝗮𝘁 𝘀𝗵𝗲 𝗵𝗲𝗮𝗿𝘀 𝗳𝗿𝗼𝗺 𝗼𝘁𝗵𝗲𝗿𝘀. I mean, he may be not sincere with his flings, but i don't think he would never do something like, make fun of her for getting her period. He even asks if that's what she thinks of him. And she also turn some things he says, worse, because in my view when he says that they're not together or having something, he was getting along with what she was about to say, so the creepy guy would stop annoying them. It really doesn't makes much sense being upset about it because they haven't even kissed yet, he was only giving signals that he wanted to hook-up with her. What is true is that he have the "Do people need to date each other?" mindset, which has nothing wrong too.
Other thing about Jaeon is that he really is a more reserved person, he doesn't talk much about himself. This way of being leaves people talking about what they don't know and imagining stuff. And i think it's intentional, for the watcher to see him (most of the time) by her eyes and the eyes of others. Also, Nabi gets anxious with this type of behavior due to her own type. We can't hear his thoughts on the beginning so we end up just like her, wondering what passes on his mind.

I see them both, as 𝘁𝘄𝗼 𝘀𝗶𝗱𝗲𝘀 𝗼𝗳 𝘁𝗵𝗲 𝘀𝗮𝗺𝗲 𝗰𝗼𝗶𝗻. Is shown that Nabi's mother is seemed by her as "neglecting" and she already had poor relationships, where the guy was a bad person but she loved him anyway. Unfortunately, we learn with our parents and end up 𝗿𝗲𝗽𝗲𝗮𝘁𝗶𝗻𝗴 𝘀𝗼𝗺𝗲 𝗱𝘆𝗻𝗮𝗺𝗶𝗰𝘀. Nabi has already had an terrible ex, where she needed a bigger issue to happen so she could leave him. And, after that, she founds Jaeon, that is emotionally unavailable. And Jaeon's mother is shown too, she's distant since he was a kid, but she compensates with money. Which might have led him to be distant in his relationships too. So, what i'm saying is that even if they have personal responsibility for their choices and actions, i can see where they come from.

None of them are saints and Jaeon have his moments of being a jerk, like when he acts stupid around Nabi and the freshman that is flirting with her. But, i don't think he's a bad person. He's a guy that is 𝗮𝗳𝗿𝗮𝗶𝗱 𝗼𝗳 𝗯𝗲𝗶𝗻𝗴 𝗶𝗻 𝗮 𝗿𝗲𝗹𝗮𝘁𝗶𝗼𝗻𝘀𝗵𝗶𝗽 𝗮𝗴𝗮𝗶𝗻, due to past experiences that isn't known much about. He even says that when you have certainty about a relationship, it becomes weak. That's why he draws some lines, as Nabi said. And, even after he asks her to date him, he cringes when he remember it. Also, I think Jaeon doesn't take much time to fall for her, but he doesn't even know how to deal with it. In my vision, it starts after their first kiss. Even his ex, Seol-Ah, can tell that something's going on with him. It's difficult to say some stuff due to the lack of information but i believe that he may has stopped seeing other girls after he realized what he was feeling. Cause, even that incident where he gets a punch, turns out to be a mistake and his ex confess that she lied to Nabi. So, i am defending Jaeon of the extreme critics he gets but i'm not denying that he has issues and can be labeled as some kind of red flag.

There's two things that i find very interest in this drama: the double meaning when he talks about butterflies and also talk about her, and the parallel between their relationship and Nabi's art. This drama is different from the others due to this type of subtle meanings. And that may be one of the reasons why people dislike this drama. But, it's so beautiful to see how Nabi gets "free" after she reconstructed her art piece. Even her professor says it to her and tells her to do whatever she wants. And that's what she does.

I think that in the end, she just 𝗮𝗰𝗰𝗲𝗽𝘁𝗲𝗱 how that relationship started, in a bad way and with them both being stupid. She accepted that she liked him anyway, that she was happier in his presence. It's beautiful when he asks "you're not gonna regret it?" and she says "yes, i will regret, of course. but i'll do it anyway". They both are 𝗹𝗶𝘀𝘁𝗲𝗻𝗶𝗻𝗴 𝘁𝗼 𝘁𝗵𝗲𝗶𝗿 𝗵𝗲𝗮𝗿𝘁𝘀 and giving a chance to love again. The prologue gives me hope that this worked well for at least sometime and that's enough. Of course, we're being more critical, i'd want them both in therapy and trying to get better. If Nabi was a friend of mine i'd tell her to be cautious with him, to pay attention to his actions. But, in general, i don't think their relationship is "toxic but romanticized" or something like that. I think it's realistic and obviously not perfect.

To end, i think one of the reasons why people don't like Nevertheless is because the drama is a 'slow burn'. It really doesn't have much scenes to leave you apprehensive, it's focused on the characters relationship. And even if i didn't mention it, the other characters are also very good to watch and analyse.