There are countless reasons for why your progress behind the kit may be stagnant at the moment. In this short post I will explain the biggest reason for this from my own personal experience; witnessing it first hand in my own practicing, and in some of my students.
PRACTICE VS. MAINTENANCE
One of the biggest reasons you may have stopped progressing as a drummer is because what you think is "practice" is really just maintenance.
By maintenance, I mean you are just sharpening and *maintaining* what you already know how to play, so you don't forget how to play it and don't lose the muscle memory for how to physically play it.
Where as practice on the other hand, is the slow and painful process of figuring out and developing something completely new to your playing.
As a general rule of thumb (not to be taken too literally):
If it sounds good, it's maintenance. If it sounds absolutely terrible, it's practice.
Hope that helps!