And as the years went by attitudes towards stereotypes changed.
Further explore the concepts of racial discrimination introduced in Bridle Gossip
or
Ignore those themes completely and invent new "safer" races to explore.
Enter yaks, griffons, changelings and dragons. No immediately obvious racial parallels outside of safe ones (YAK TALK LIKE THIS, VAGUELY MONGOLIAN???)
But that's exactly what happened.
"Hey...where are the other zebras?"
For the racial sanitization hat trick to work Zecora's lonesome existence can never be questioned. Zecora herself isn't even allowed to show any feelings about it, happy or sad.
The nuanced themes of Bridle Gossip were replaced with a cartoonish caricature (Professor Neighsay) and hamfisted liberal ideals (RACISM BAD)
Its a quaint sort of thinking that seems dated when compared to more ACTUALLY progressive shows like Steven Universe or She-ra.
Corporations, despite their attempts at pandering, are not your friends and don't give a crap about minorities whatsoever.