Good progressions!
I mainly think your renderings look a bit flat. A few sharp highlights often do help pop the shape more, if done well, and depending on the entire lighting environment.
I feel that you need to draw more based on the light that would reflect off of the surface based on the lighting, and less in a 2D fashion - even if it’s a side projection. Now you add some shadow and highlight here and there, but it could be better in accordance with the overall shape. That would really make the drawing readable as a 3d form.
The drop shadow in the second one is better, make it even darker just under the sole - it could almost be thin like a line. Study how real shoes look in a well-lit/studio environment!
I am also liking your designs, maybe they could be simplified more and made a bit more coherent overall. I wonder if Adidas stripes can be that thin, it’s quite critical - this looks almost like an imitation to me.