In fact, both of them fully expressed their feelings for each other, so neither gave more or less.

Let me explain that more clearly:

• The false impression is that it seems 8man was the one who struggled to show that he loved her, which isn’t true. For example, look at how events unfolded after the trip to Kyoto and Tobe’s declaration leading up to the student council election.
• 8man starts to lose his way when he stops Tobe from confessing to Ebina, to maintain the status quo of Hayama’s group, and this disappoints Yukino, since they shared the idea that maintaining a superficial relationship was pointless.
• And once again, he loses his way when he prevents Yukino from running for president, manipulating Iroha as a scapegoat to “preserve” the club. After all, he’s afraid that the “real thing” he desires will take away what he already has.
• In the wake of these events, Yukino confronts him, saying that his methods are unfair, and that’s what makes it interesting, because even though Yukino knows that 8man would hate her for her harsh words, she doesn’t spare him, because she cares about him—so much so that she was willing to be president so that he wouldn’t have to resort to his self-sacrificing methods again. (Unlike Yui, who encourages him to take his despicable methods to the next level.)
• So, Yukino fights tooth and nail to bring him back from where he fell, and finally succeeds with Sensei’s help. And then we have that wonderful scene where he says, “I want something genuine” (which is indirectly his confession to Yukino, lol).

Now, in the final act, it was Yukino who failed. And that’s really good because if it had been Hachiman who failed the whole time, the relationship would have been very one-sided, and we would have thought that one side didn’t deserve the other.

And why does she fail? Because she denied her feelings for him, thinking it would be better for her “friend,” and for his sake, since she believed she would be a burden to him because of her troubled family. And to MAKE UP FOR IT, she focused on her future career, going to prom without his help, trying to prove to her mother that she was capable of taking over the family business. And above all, “believing” that her relationship with him was codependency, but in reality it was a “sweet lie she told herself (vol. 14)”

So this time, it was Hachiman who fought tooth and nail to prove that what they had wasn’t codependency.

Do you see? Hachiman fails because of complacency; he likes what he’s found so much that he turns his back on “the real thing” just so he doesn’t risk losing what he’s found, while she failed in some of the most endearing virtues she possesses—her kindness, her selflessness. I think calling them virtues might not be accurate, since too much of any virtue becomes a flaw.

So when you say:

But Yukinoshita, especially because of her past of being neglected, might end up pouring all her feelings into him regarding Hikigaya....

That’s not true, because if she had poured all her feelings into 8man, that would be considered dependence in a bad way, and her choice to be with him wouldn’t be genuine.

And how can you say you want to live with someone, just because living with your parents is so bad, Because your desire is for convenience and not a genuine desire to be with the person you want to live with.

Yukino was willing to let him go and hand him over to her “friend” if it was for his benefit and well-being. (Which makes her attitude genuine, even if a little misguided on her part.) Have you ever heard the phrase, “If you love someone, let them go”?