I feel like a lot of hate towards Tracey is thanks to how popular and influential Cori Falls was in the fan fic community becaus while Brock was popular, sure, most kids just really didn't care too much for Tracey to either love or hate him. I don't entirely know if it was planned from conception, but Tracey's goal was basically to work for Professor Oak, his idol, and so at the end of the season, he got that wish, and that's where he stayed to be his aide. The last time he had any kind of role in the series was Chronicles, but after that he was just demoted to the background, which is appropriate, but it's unfortunate he's otherwise a wasted character.
I haven't been keeping up with the anime as of late, so it's honestly disappointing to hear he hasn't actually appeared in person for quite some time. I agree with the comment(s) saying it's most likely due to his voice actor being unavailable, but that doesn't mean he can't have a voiceless cameo. Unless he's off running errands for Oak every time the corral shows up, that's a real shame he's being quietly phased out if that's the case. Seems to have occurred a lot for previously-recurring characters (such as Butch and Cassidy) since around Best Wishes.