I have a really hard time seeing shadows. I like to attribute this to having lived almost my whole life in Oregon, in the Willamette Valley, where we have overcast, rainy days and can go for weeks at a time without seeing shadows. This doesn't really work as an excuse for indoor scenes.
Shadows are hard for me to draw partly because I've always been much more focused on line. I'd like get better at seeing shadows, and colors, and reflections---and line!
Here's my current skill level. Among other things, there are definitely problems with shadows and ellipses. This is my baseline. I'll come back and check in a year to see if I've improved.
In this sketch, the Lindor chocolates are covered in foil and then cellophane, but I have no idea how to paint reflective material like that. I did notice that even the cellophane cast shadows. Who knew?
The amazing thing about this sketch is that I didn't eat any of the chocolate, even after I finished drawing it!