They stopped literally because the creators of the show had to come out and reassure race baiters that these black Targaeryens married and intermingled into the Targ family. This allowed these "critics" to dismiss them as "not really Targs" so who cares at that point.
Also, being a moderator doesn't mean I don't have an opinion. And my opinion is firmly that casting actors of particular races only matters in pieces where the race is an integral part of the character, or historical pieces, and only then if the historical piece is going for accuracy. I didn't care when Michael Jackson remade the Wizard of Oz with black actors, and I didn't care when they made a musical play called Hamilton about the Founding Fathers with black and brown actors because......well, it was a rap musical which took liberties.