depends on the isekai's setup. mushoku tensei, dr elise (to an extent)? it's about redeeming yourself after you got "unlucky" and never rectified yourself. black company isekai like death march, by the grace of gods, or i shall master this family? it's about the desire to prove your worth and be loved/respected by others for the effort you've always put in. illness isekai like leadale? it's just a fantasy about being able to do whatever you want, because before you couldn't do anything. eminence in shadow? no deeper subtext, MC is a fucking chuuni and watching him wreck people is just fun

the death aspect is less about desiring death and more about wanting a total reset