The problem with this is that while SV is a fantasy world, not everyone can use it to escape real world problems in the same way. Lack of diversity, and being against changing that, is a real world problem. POC play Stardew too and deserve to escape into fantasy. It seems that you are able to step away from how diversity/lack thereof impacts you, but that isn't true for people who aren't white. (Also, Stardew definitely does deal with IRL things. Addiction, depression, an abusive familial situation, the press of capitalism - those are big story elements!)
Of course no media can represent everyone. But if media all did a little bit more, then it would end up making a big difference.
I get that this would not be a quick change. But I think it would be one that would be worth it. Stardew Valley is a great game and allowing more people to see themselves in it could only add to that!