Is my community my favorite subreddit, or my physical neighbors who are actively voting my rights away? Should I support my country of birth and residence in a trade war that damages my partner's family and her country of birth? We have a duty to protect the best parts of our communities - does that mean I should or shouldn't accept that job to work on nuclear weapons? At what point is it just to emigrate to NZ rather than stay and try to work toward solutions? My family is literally divided on this point, with several members now enjoying a covid-free existence on the south island.
These questions didn't really exist 2500 years ago. The boundaries of human communities were clearer, in my view, mostly because there were hard barriers to emigration and global communication. But to your point, that doesn't mean the fundamental principles have changed, and maybe things aren't all that different after all! We just have to be comfortable with asking and answering our own questions and applying principles to our modern times.
Is that actually outdated? There are fewer "entire community mobilized against existential threat" type wars these days, but there seems to be a constant brew of conflict world wide (proxy wars, drone strikes, etc). Frankly, I find Stoicism one of the best ways to cope with the two quotes I keep hearing in my mind: "high school never ends" and "war never changes".
Finally - We're just on the very tip of the cusp of the effects of climate change. Entire regions supported by subsistence farming for millennia will within a lifetime become a literal hell. As we go from a world of seemingly endless abundance to constrained resources (arable land, potable water, etc.) I think "war like city states" more closely represents our future than anyone really wants to accept.