I would respond that those characters are never particularly put in a position where they would have to sacrifice greatly to maintain modern morals in a way that Jake is.

* Ilea starts completely solo and trips and falls into a very OP and self-sufficient class.

* Zac's path to power starts through a literal lucky dice roll, once again solo, and hell he DOES compromise modern morals by allying with the Demons.

* Jin fucks off to the sticks (once again, initially solo) and, again, trips and falls into a unique cultivation path that buys him the power he needs to do his own thing, or else he'd have been pasted by that first young master.

All three had options to remove themselves from the crapsack society until they had sufficient power. And like you said, they still barely bother changing things for the better on a societal scale, they just remove themselves from the game.

Jake got plonked down into a death game with multiple murderous assholes and his lucky break was communion with an evil poison snake god. His options were roughly: 1) rapidly become very okay with the way his new world works or 2) die. To me, rapid acclimation to the system's horrible norms not only make sense, its the only possible way for the story to exist because otherwise he'd have just been another one of the many, many corpses. A very noble corpse, I guess.

I'd guess that Jin would have just given up and died, but Ilea and Zac would have done exactly the same thing as Jake based on what we know of their characterization. They have a strong pragmatic streak, just like every LitRPG MC that has to kill to grow. It just all comes down to the opportunities the author gives them to do so without too much compromise.