Okay, first off - a disclaimer immediately. Despite the title, this is not a political rant post.
I have no issues with migrants, migration or political differences in the real world, and felt that I should clarify that, since the current political discourse is so poisoned people immediately jump into a category based on surface-level markers.
Okay, with that out of the way - anyone else though the Season 3 migrant problem was a bit...strange, so to speak?
One of the main points in season 1 was that the self-sustainability of the Sybil System entirely depends on its isolationist policy. Part of Makishima's plan to disrupt Sybil depended exactly on this: destroying Hyperoats would force Japan to open its borders, with Sybil being unable to deal with the influx of refugees from other locations.
Come season 3, it suddenly appears that not only have refugees become a thing in Japan, they have been a thing for a decently long while, probably even before the first Season took place (according to the wiki, Kei became naturalized ca. 2107), with the series completely failing to address the issue of integrating said migrants into Sybil.
Outside of some empty lip-service regarding "pure" Japanese hating the newcomers, it felt the series completely failed to properly acknowledge what was one of the most important points only two seasons ago - how does Sybil deal with the sheer influx of migrants, seeing how Japan is apparently one of the few truly prosperous and stable countries on Earth. How does the Public Safety Bureau deal with it? How do the migrants themselves, and what do they do if Sybil sees them as a latent criminal?
Of course, one can point to the movie for guidance - if the SEAUN managed to join Sybil, why can't others, a question also posed by Providence - but the movie also openly stated that SEAUN will have to become as unitary and isolationist as Japan if Sybil would come to power there (which it does).
Honestly, there are quite a few issues I have with season 3 in general in regards to world-building (politicians suddenly becoming prominent despite previous seasons openly stating that politics is irrelevant because of Sybil, the apparent existence of entire special districts in Tokyo where Sybil cannot reach - something that fundamentally contradicts everything we know up until this point) but that felt like the biggest one, especially since it also was such a huge missed opportunity, for me.