Well, if I'm just speaking for myself, I think Min Min is a cool character. I really appreciate that the Arms team gave her a decidely chinese flair - with her name, her clothing style and the graphic details, the food, her eyeshapes, and she speaks chinese (with a japanese accent). The fact that her silly noodle hair is blond, at least to me, is not a huge dealbreaker to accept her as chinese.
It might surprise Westerners but chinese people also have modern technology like electricity and hairdye ;)
And even if she was a danish girl that just really likes chinese noodles, I still think it's a cool chinese representation.
What is also interesting is that she's one of the few characters in the roster that are actually tied to a specific "nationality". You've got Mario&Luigi (italian), Ryu & Joker (jap.), Terry, Snake & Ness (USA). I don't know if Simon and Richter are supposed to be romanian? Anyway, I think she's cool.
Having said that, Twintelle would have been an awesome addition as well. OP is completely right with this thread, and it's frustrating to see A, how Nintendo has handled this and B, how few black skinned characters would be available in the first place. When it comes to black characters, Smash is really the symptom of four decades of compounded neglect and ignorance at Nintendo, but also in the whole industry. And I guess if you look at four decades worth of IP at other longtime publishers, be it Sega, Atari, Sony, Microsoft, Capcom etcp, it's probably not gonna look much better.
Videogames have a long way to go.