JII was delayed several months because of issues with the turntable scene and vehicle timing associated with it. While they did improve it, it was never fully fixed and vehicles would constantly speed up, slow down, or just stop altogether from what I've seen in videos. It wasn't perfect, but it was enough to operate. The unload belt was removed after a few years because of those timing issues leaving the vehicles at different speeds than the belt, so they just replaced it with a stationary floor. If you look at YouTube videos, you'll see the ride speed up and slow down at times. The ride itself also was prone to breaking down because of said turntable from what I've heard, which is why they removed it and 40% of the original track when they made JIYI.
In the long run though, it didn't affect the rides popularity by any stretch of the imagination!