Yeah but isekai is boring only because it's lazy and worn out. Slaves is disturbing because it usually is justified by the enslaved somehow deciding they want it after the fact. Like, consent doesn't work like that. The MC is still a slaver.

It's so absurdly easy to let the hero be a hero, save someone, then they can follow the hero because they've lost their party or need help getting home or whatever. It's dirt cheap without the ick.

shit, be lazier than my dm, just have the character say they've got nothing better to do, why not follow a stranger? Save back story for later, and retcon why they had nothing better to do after the fact.