I actually had a very, very different impression. EA seem to be going above and beyond trying to include different cultures and ethnicities, and they keep on adding.
Take for example the Cottage Living expansion pack. It was based on an English farming village. In reality these villages have remained entirely Caucasian because the populations are so small and made up of families (there's one down the road from me with a population of only52). Besides that, people generally don't relocate to the middle of no where just to work in a corner shop or as a labourer on a farm, hence no diversification over time. It's sort of funny that EA made Caucasians a minority lol
It's nice that EA have introduced diversity into the type of places where there was traditionally none (in the latest EP), but I suppose I agree with you that the Island Living and Snowy Escape worlds are not so diverse. Maybe it's best to just enjoy playing the game.