...and then i realized your sketchbook thread is f-in 4 years, stretching 2009-2013.
mind is blown.
One technique to work around a barrier is to make drastic changes in the way you work.
You probably have a specific technique for how to output a painting complete with your default way to make the composition, structure the piece, build the characters and do whatever color work. Part of your inability to break your barrier is tied to your conditioning with those techniques. In other words you've learned an error and its hard for you to un-learn it.
If you take a different technique, a different medium and draw in methods you are not comfortable with, you won't encounter the barrier of the stuff you've already learned in as strong a way, and you can focus on learning whatever you're not succeeding with "the right way" without having yourself as a disruptive element.
and after that your new understanding should be easy to incorporate into the rest of your work since you already have the idea that what you're doing now can be improved.
When i look at your work so far I don't see that you work with oil pastels. I think that's a good way to start. Oil pastels have a different feel to them than other mediums, they require you to "play dirty" and touch the painting to the extent that your hand gets sore from doing art, they generally have a very rich, vibrant natural color (which is what you're struggling with - giving your work these qualities) and don't allow you to get easily into any decent resolution - meaning you'll have to work your ass off to get into the amount of definition and that pushes you right into tackling your problems. They naturally lend themselves into being mixed into other oil pastels (with some coercion) Also they are cheap.
The heights by great men reached and kept,
Were not attained by sudden flight,
For they, while they companions slept,
Were toiling upwards in the night"