You're still sort of relying on texture, in the sense that, in the example workflow you gave, the black color-ramp alone used like 6 colors if you include the black outlines. Try forcing yourself not to do that, working with only 3 or 4 colors and trying to achieve a cel-shaded look. Focusing just on the stomach-region of the animal, your shading seems to be almost a gradient; you're trying to shade realistically but in reality you're just picking the side of the silhouette closest to the lightsource and then generating a gradient based on what you consider the light end and dark end of the shape. Focus on form; force yourself to draw in terms of concrete lines differentiating the light sections and dark sections, instead of your current wibbly-wobbly attempts to avoid committing to discrete regions with texture and weird almost-dithering techniques.
Consider using less outlines as well. On sprites that small, an outline is a lot of space, so to speak. You can still achieve meaningful separation of regions by making them different in contrast and color, removing the need to use the blunt sledgehammer-like tool that is heavy outlining.
Generally speaking, outlines are part of the work itself, but you seem to be rendering them as if they were separate from the internal coloring- a phenomenon which seems like you're 'afraid' to touch the sacrosanct lineart. Don't be! Lineart is there to help your readability, you don't have to color 'around' the lines or anything. Consider trying some sel-out techniques or even making line-free designs.
Also, I'd recommend you not use NPA tools like luminosity or overlay layers for the moment. Practice working with pure pixel tools; by limiting your own toolset, you restrain yourself in the same way that martial artists might go about their day with training weights. When you get used to limitations, you'll suddenly find that your usage of NPA layers will go from being a crutch you leaned on to a tool that you can utilize to true effectiveness.
(Also, don't be so nervous! It's kind of obvious that you're obsessively formatting your posts and trying to look neat and professional, as if you were presenting yourself in tuxedo to some sort of highly formal event. Don't bother with that, lol. Make yourself comfortable and relax, Pixelation isn't a place with tons of in-group cliques and unspoken rules or anything like that.)
