I think Joobin did have feelings, though they could never blossom fully because of all the insecurity and also knowing full well that Baek-Un was using him as a stepping stone and therefore their relationship was transactional, but I do think everything else was spot on!
Thanks! So I tried to look at things from your perspective and ig it does make a lot of sense. Joobin was closed to falling for Baek-Un but he never allowed himself to fall for Baek-Un because he was afraid of separation and couldn’t let go of his first love. In ch. 67, Baek-Un tells Yikyung that after they break-up, he would need at least one person to talk about that with. He’s assuming that Yikyung will go through what he has gone through (loving someone who rubs at your wound and won’t love you back). Then when he met Joobin at the elevator, he says “Do you even like this guy?” To which Joobin replies, “I love him. Have we ever said that to each other even once?” He’s stating that Yikyung is different from Baek-Un because this time, he allowed himself to fall for someone other than Sehyun. Then in Ch. 68, Joobin says this: “I always admired how predictable you are. I always took comfort in knowing that you put yourself first. If you haven’t broken up with me that day, I would’ve kept hoping that one day you would come to love me, despite the fact that the things you love are things you can never have.” What Baek-Un wanted was an unmasked version of Joobin, a Joobin who would love Baek-Un back. But Joobin can never give him that because he was still hung up about his first love and took comfort in knowing Baek-Un won’t replace Sehyun. And adding on, maybe that’s another reason why Joobin apologizes each time he calls Baek-Un’s name. He saw a piece of his heart that belonged to Sehyun get taken over by Baek-Un. So when he apologized, he returned that piece back to Sehyun, preventing his love for Baek-Un from ever taking form. This leads to the next statement that Baek-Un makes in Ch. 72: if he had known the meaning for why Joobin apologizes, maybe their outcome would have been different.
I had to read these two chapters a couple of times but I think I got it. Their relationship was always destined to fail because Joojin wanted someone who would prioritize him and Baek-Un can never do that. It took Baek-Un and Joobin too long to figure that out, leading to them being unable to cut each other off and continue to harm each other. The only time that Baek-Un expressed his love for Joobin was their drunken night together. Joobin never liked Baek-Un but kept up the charade because he wanted someone to love him. He knew Baek-Un wouldn’t “break up” with him because he was in love. He would call Baek-Un’s name affectionately but apologize shortly after (due to guilt for playing with his feelings, and that’s why Baek-Un wanted an apology). Since Baek-Un only ever prioritized himself and knew Joobin was putting a wall between them, he was too afraid to show his love. (“Even though I [Baek-Un] was the one who was always waiting and asking for comfort”). Joobin was shocked from the confrontation with Baek-Un because Baek-Un denying his feelings meant Joobin won’t have the one person, at that time, who was closest to fulfilling his ideal - a person who won’t ever abandon him. Earlier chapters already established that Joobin wanted love from others — testing them constantly, and would cut them off if they can’t give him that — but had only ever fallen for one person (his first love) before meeting Yikyung. I think my interpretation’s pretty solid but what do y’all think?