From a new player's point of view.
I don't think sliders are so easy. This is my 5th of play and I improved a bunch since the 1st. However as I tried to perfect my mechanics, by playing easy maps, I was "stopped" by Xhroria (Easy, 3 stars). I got 299x instead 300x (full combo) 3 times in a row without understanding why. Since I got S with +95% accuracy on first try I thought : "What the hell can't I FC this song ?"
The truth is I didn't know I was missing the end of sliders. In certain patterns I held too shortly, because I never focused on this aspect. Some reasons why I was missing :
* short transitions, leaving too fast
* returning sliders, leaving too fast
* joined sliders with different lengths : reading |--->|<---| instead of |----><--|