Stellaris will only have its AI fixed in June-July, so now I play the "New World Order" mod for Victoria 2, which bring the hilariously broken economic system from Pop Demand Mod into the modern age. Diplomacy is also hilarious - EU doesn't even exist, the first thing Germany likes to do is attack Belgium and Poland for rightful clay, Spain attacks Gibraltar every single time, etc.
Immigration system was written by someone from /pol/ - if your country has enough social policies, you will attract thousands of Arabs every other week, who don't assimilate, raise militancy, rape women and boost the popularity of right-wing extremists. The only way to stop it is closing the borders and removing kebab, but then say goodbye to your population growth and relations with the rest of the world.