The one-drop rule was a way to keep a person who had black ancestry as black. Even if the ancestry was 3 or more generatons removed.
Now a days, if a character is half black and half white, they are considered black. Kristen Bell, who is white, represented half of the characters ancestry, but people said that this character was black because the dad in the show is black. This mentality was, rightfully so, considered racist in the past. Yet we now see it being enforced in hollywood and other mediums.
Just to drill this point home, this is a cartoon. Who cares what color the voice actor/actress is in real life. IT IS A CARTOON. This attitude has really made it so I can’t just enjoy a show.