Sex is not objectively good or bad based on how long it lasts or how big it is, but like food, everyone has different tastes. MC could be Jamine's type.
For Julia, think about the other partners of Cornell. Most of them are having relationships with Cornell with their husbands' permission. Maybe Julia will stay in this relationship, or maybe she and MC will go to Cornell's house together and have a threesome time to time.
I also think that sex is not everything in life. MC could satisfy her with a toy or tongue instead, and she could be satisfied with that. Love matter, man, love matter.
It's a little strange to hear that word "love" in these games and in this one, Julia shows an interest in Connell from the first moment, which I think is evident, Julia decides to help him, Julia never stops Connell beyond measure if there wasn't the password of MC, Julia of the 4, is the one who practically never speaks, and when it comes to Connell's moves, she never takes a step back, Mc goes with Jasmine, of course, but the primordial concept between man and woman is different, a man, even if he doesn't look for it, still doesn't miss a fuck that is easily thrown to him, a busy woman on the contrary, would think about it several times, or at least make things less evident, I don't justify MC, I justify the situation, which is different, Julia from the first moment we see that she feels at ease with Connell, then the various paths vary based on our choices, but the basic point remains, Julia has an interest in Connell, perhaps Jasmine pushes for her interest, but whoever tells us that in the long run she is attracted to MC, grasps the situation by throwing Julia into Connell's hands so that MC stops loving her, considering, here we have everything, except the word Love.