Why do you make it sounds like this is not what they have been trying to since forever? Slavery like Robots and Purges are something the AI will never do "exactly as you would do it". They implied some general rework of the whole slavery/purge mechanic. To make it better controlable in a Large Scale Empire.
I assume you are either joking or have not tried to use slavey with sectors. When then AI enslaves EVERY PERSON ON THE PLANET that means that the functionality is fundamentally not working. It isn't a case of "oh the AI isn't doing it exactly as I want it to" as you incorrectly stated, it a case of the AI literally enslaving everybody and hence preventing slavery from being used as it should be in sectors.
Also FYI your "just make mineral sectors" comment is also very dismissive of the issue we are discussing. Planets should be able to have slaves and non slaves. Also, people don't don't want just mineral sectors. Some sectorsneed to make energy and some need to be dedicated to research, quite simply. As you grow larger you can't just have you core planets alone doing this for you.
Its a shame that you, like some others, are completely dismissive of obvious flaws in the game.