Yeah, but would you be able to live with a partner like Jaye for the rest of your life if she keeps behaving to you as she has? Which would be the logical assumption, since MC will not be perfect in future either and make mistakes, misfortune will happen and he will have to talk to some pretty women as well once in a while, whether he wants to or not. While Jaye until now has not shown any signs of a change or even awareness her behavior is a problem for MC.
(Now that would be no problem for a heavy competing story line, where bro and sis try to seriously hurt and kill each other while secretly loving each other and being unaware they do, but at a certain moment it will for the opposite especially since at least from MC's perspective it already escalated enough for him to want her out of his life.)
That is what you Jaye defenders at any cost are asking MC to do, he has little to no reason to think she will ever change and just finally recognized her behavior might be partly jealousy. Especially since her behavior did not change after being not affronted by his company for 5 years, during which he preferred to not have her company in his life for exactly those reasons (five fucking years, it is not like MC slunk away and sulked for a day).
MC at the moment still has little or no reason to want her in his life beyond the fact he loves her and she is his sister and needs to balance that with the impact her behavior has on him and we know what decison he made in the past regarding that exact question for the last 5 years.
By the time she finally admits she loves him, poor MC might well be so traumatized he does not give a fuck anymore and just wants her drama as far away from his person as possible, every normal person who is not a total masochist has a breaking point when it comes to constant drama in their life. (Beyond the fact this is a game and plot armor likely would not allow MC that if you are on her route, but as a player my disconnect with MC may well become to big way before that moment.)
It is not for nothing the Chinese curse is may you live in interesting times and MC's life is certainly way more interesting whenever Jaye is around him.
The thing is not that Jaye is always wrong and MC is always right, just that a happy relation between them is pretty impossible if Jaye keeps behaving as she has and is (whatever MC does now, even turning into complete and perfect Simp that will do everything possible to not ever ever ever annoy her in future from now on, at which with his talent to annoy her he would most assuredly fail once in a while).
Bringing Rapey to the boat would be great drama for sure, but also would escalate her behavior and confirm it in a way that players like me would need to see at least the seed of a serious turnaround quickly in her to ever believe such a relation could ever work from MC's pov and with me playing that MC.
There is already enough drama and past between those two that it would be a long road even if both tried to change their behavior, since there would be some fall backs on either side, even without escalating it further with Rapey. It is not like with their past a simple I love you from both sides would be enough to take all that hurt, uncertainty, insecurities and distrust from both sides away without heaping even more on it with Rapey drama.
That is also under the assumption no third character in game might add extra drama for their own reasons (looking at you Mallory) or has reason to keep those two apart.
Those two will need some time and hard work from both even when they accept they love each other, to make it work. MC is too talented at annoying Jaye and do the exact wrong thing around her and Jaye will not suddenly turn into someone who starts to think first and not act out her jealousy and insecurities when comes to MC immediately without thinking about it once in a while at least .Besides for both goes that forgiving the past is way easier as forgetting about it. So there will be fireworks enough anyway even without bringing Rapey in, if they finally do decide they would like to be together and both will try to change their behavior to each other.
