Groove
The difference between a good drummer and an amazing drummer is often not in the patterns or fills they are playing them, but how they are playing. The way I tend to think about playing is that there are no bad ideas, there is only bad execution.
For me the one thing that really decides how well you play is Groove. It is so important for all styles of music, I tend to think of it as the difference between playing a beat, and performing a piece of art.
Groove can be split up into three discrete parts:
Tempo
Tempo is the speed of the piece you are playing, it is considered most of the time to be the drummers reliability to ensure a song starts and remains the correct speed for it's duration.
But for most drummers today tempo goes a little bit deeper than that, tempo is about making sure that you are aware and in control of the speed you are playing the whole time you are behind the kit. This doesn't mean not being allowed to speed up or slow down, rather that you can achieve whatever you want to play, as opposed to what you are playing dictating the speed to you.
The only real way to achieve proficiency in controlling your tempo is to play to a metronome. Playing to a metronome can be a valuable tool to aid your playing skill.
Some people dislike playing with a click, claiming it stunts your creativity and takes the feeling out of music, making it sound robotic.
But why does it have to? For me a click is something that you can use to help you, even if you don't play to a click all the time working one into your practice routine can help make your internal clock stronger.
Pocket sounds like a funny term, but it is essentially the way that you interact with the other musicians you are playing with. It is possible that you could be playing completely in control of your tempo, but still sounding messy because you are not 'locking in' with the other musicians playing.
It's still a part of timing for me, but it's about being sensitive and responsive to what others are playing.
The only way to really work on pocket is to play with other musicians. Nothing else will be able to prepare you for trying to get into someone else's head and know what they're going to do next.
Feel
Feel is the last piece of the jigsaw, it's all about how you control the patterns you're playing. In the same way that pitched instruments use different tones to incite different emotions from the listener, the drums don't necessarily deal with emotion, but they can have a great effect on how the listener perceives the piece of music.
For instance, during a slow guitar ballad, you wouldn't be likely to put in lots of fast fills using 32nd notes and complex rhythms, the song wants space to make it more emotional. Putting in gratuitous fills will ruin the slow feel.
Or in a fast tempo, you probably wouldn't use half notes or whole notes in a fill the whole way through a song because it would completely drag all of the energy out of it.
Also the way you control the subdivision, you can play 8th notes as Straight, or Swung or as a shuffle. You can do the same with 16th notes, it's all about the spacing between two consecutive notes. But tying this into groove if you start a song with a swung 16th note feel you want to make sure that every beat, every fill and every rest are all within that same subdivision feel.
You also have to bear in mind that you can drive a groove by pushing against a click, making something seem faster, or you can relax against the click to make it seem slower, or strive to make the time as spot on and reliable as possible.