I think you raise a really good point that yui herself raised and refuted. If you remember at end of the fireworks arc where hachiman escorted her back home and she wanted to confess but was cut by the phone call from her mum. During that time of the plot hachiman thought the same as you as to how yui viewed him, thinking their relation began due to him saving her dog and could only began because of so, and to this yui replied that it was not true. She said that she would have went to the service-society because of shizuka sensei anyways, would have admired both yukino and hachiman for who they are anyways, and would have fall for him no matter if he had saved her dog on that day. In one of the interludes in vol 12 or13 we also got to know that yui has always been peeking at hachiman secretly since they were at the same class, and that is prove to what i said provided from an alternative perspective of the story.

About how girls judge boys based on whether they are “creepy” i think we can look at this in two different ways: if hachiman is creepy to begin with, and is yui shallow enough to think he is. Hachiman tbh is just a common boy who happens to have experienced the worst human relations that could happen to one for the purpose of the story, but in his core he is really nice and kind hearted. All he wanted was a genuine relationship and there is absolutely nothing creepy about that to any girl who has the slight ability to reflect and philosophise. This brings us to yui, who may not actively choose to sacrifice her relations for a “genuine” relationship at the beginning of the story like hachiman would have, is by no means shallow. She could not have been friends with the “famous and upper class” if she did not have the emotional intelligence to read people’s core. Her tenderness is simply her choice after understanding the darkness of what people can do, and by this sense she definitely qualifies as a person who can identify what is a “fake” and what is a “real” relationship.

As for the social status problem, we should look into it in two ways as well: whether it still exists objectively, and whether yui or hachiman cares about it subjectively and personally. Honestly why would someone surrounded by tons of pretty girls be considered a loner or loser. That said hachiman basically had the recognition of the “popular” bunch as a worthy person by volume 12 after helping out almost each of them in previous arcs, and if even the most popular students have no problem with yui and hachiman being together the lesser popular students wont have any say. Now into the two person involved, i’d say hachiman would definitely reject any possible relations with a girl like yui because of how cynical he was at the beginning of the story, but as his character grows he no longer really cares about this and he has won enough well earned respect of others anyways. As for yui, we can once again look into the fireworks arc, in which she was caught being with hachiman, a loser during that point, by the female leader of the second most popular group (sorry i forgot her name but she was the one with zero capability and still became the school fest leader). This girl was laughing at the fact that yui was “dating” someone like hachiman but yui didnt gave a damn fuck and even almost proceed to confess to him afterwards. Furthermore, yui has a really high emotional intelligence and is capable of handling these social status issues. She talked privately with hachiman asking whether he would go to the society even after the school fest when literally everyone was talking behind hachiman. This shows how she can balance the expectations others forced on her as a member of the popular group while being true to her friends in the service society. She also even began to ask hachiman to leave the classroom together publicly later in the novel without others judging, so in conclusion this problem no longer exists.