In the 11th episode, when Takasugi told Ginpachi-sensei about how the AU didn't make sense to him, and Ginpachi replied sth like there's nothing wrong with that, and live and let live, and finally convinced Takasugi to come to school, as in, it's okay to just let go and have fun, no matter how ridiculous their situation was, it was as if it was at that moment that Takasugi decided to give in and enjoy the 3Z universe.
However - and you're probably say that it's a reach - I do believe that it wasn't as if that was the decisive moment that made Takasugi change his mind. Imo that change was made gradually throughout the series. The waking up scenes were what made me think that:
At first Takasugi woke up on the floor. Twice. Before he went back to sleep, still on the floor. You can agree that's not a very comfortable way to sleep. So the third time he just went back to bed, finally accepting the comfort of a mattress, like a normal human being.
Then with the school festival episode, when it was revealed that he just slept through the day and completely missed the festival. He just stared at the calendar like, "oh, I really missed the school festival". I wouldn't say he was filled with deep regret for not being a part of it, but maybe to some extent he understands that there are things that he's expected to do in that universe, like a normal highschooler, even if it was just hanging with his gang at the festival (I assume Matako was the one who wrote that note on the calendar).
Also, there was also that scene in the MonHun episode where Matako (I think?) implied that Takasugi wouldn't skip school so much if he just woke up in time (a reminder that in the Ginpachi-sensei snippets in the OG Gintama anime Takasugi was actually very often present with the rest of the class). So it wasn't as if he *didn't* want to be part of the 3Z class, that's just how things wound up after his "suspension" (whose reason was revealed that it wasn't even because of something he did but rather the staff who didn't know how to write his character in a comedy anime).
Soooo Takasugi was actually already getting accustomed to his new 3Z life. But Takasugi being the old self-flagellating Takasugi, maybe he couldn't forgive himself for accepting such a peaceful life. Just like how he reprimanded Gintoki when they met for the first time after the joui war in the Gintama anime: "Looking away from the past and living a carefree life. You've lost your fangs to indifference, you couldn't understand how we feel."
Which brought the entire tirade about him not accepting the whole Ginpachi-sensei 3Z class grift. Was it truly a rant against the good ol' capitalist pigs exploiting every IP till the last dollar it can earn (which is also a very valid rant NGL), or a sword aimed at himself for his own enjoying of a sweet, peaceful life, for once?
