Can't turn everyone into Han anymore

Ever since SOI the migration has been reworked so that I can no longer make every province I own culturally Chinese. However, things have got even worse when POE came out. Now I can barely turn mongolia into Han, not even mentioning any of my colonies. It's especially painful for me because now my empire cannot be ethnically pure and I have to deal with all this discrimination instead of replacing native populations with my hard working peasants. Is there a way to make things like they used to be or perhaps my cultural map will forever be stained with undesirables?