I gotta disagree here.I love the mod, but I was honestly disappointed by two things: the first is that many tracks were already present online (gamebanana) for some time, so they can be downloaded and tried individually.
The fact that you were only able to replace existing tracks when trying stuff from Gamebanana was the real dealbreaker.
CTGPDX never claimed to provide "new tracks" that nobody ever saw but instead the main "selling point" (lol) is that they figured out how to add tracks on top which is super amazing imho.
They also playtested all those tracks for many month to be sure there are no game-breaking bugs because in many custom tracks I tried from Sitbar's modpacks there were bugs where you would fall of the track and result in an infinite resurrection loop from Lakitu.
They also added the speed-o-meter and a few other nice HUD gimmicks.