According to Bulbapedia, there was an interview done by someone from the Pokemon anime production, and they said that the reason why Brock was replaced with Tracey during the Orange League season was because they thought people might call them racists. However, even after Tracey was in the show, nobody really cared. Rather, lots of viewers missed Brock, so he was back for the Johto saga and beyond.
But while Tracey was in the show, do you think he fulfilled the anime creators' wish? Do you think he was a good enough character?