It isn't a stroke, a serve, a receive, or footwork; it's the ability to learn and improve. Most players play "in the moment" - they mostly play matches where they play to win now. They avoid their weaknesses, thereby not improving them; they set up their strengths in the ways they always have, thereby not learning new ways to do so; they try to win with what they currently have, thereby not developing new strengths. They probably use the same serves and receives that they've used for years.
There are times when you need to play to win now, such as important tournament or league matches. That's when you play to win, period. But the ratio of times you could be developing your game versus when you need to win now is probably 100-1. This doesn't mean you play mindlessly or without tactics; it means you should often (or always!) play tactics with the techniques you are hoping to develop, so you can develop those techniques in match situations.
Many times when players from our junior program play practice matches I'll talk to them, asking why they aren't using the more advanced techniques they have been developing in practice. Invariably they'll say they are scared to use them. Invariably I respond by asking if they think they have a better chance of learning to do those shots consistently by using them in practice matches, or by not using them in practice matches. I then say, "A practice match is practice, and if you can't use what you are learning in practice, when can you use them?"
Take a step back and examine your game. What techniques do you need to develop so you can improve? Imagine what your game should be, not what it is. Then practice to develop those techniques that need developing, and use those techniques in games until they become strengths. Continue to do this every step of the way, for as long as you want to improve. When you decide you no longer want to improve, you can always stop!