your shading technique could use some work, luckily that just takes practice.
I would look up general art tutorials on how to shade objects/primitives and study how light interacts with surfaces and casts shadows and things like that. The reason I suggest this is because you seem to be shading towards the edges of the object, so it ends up looking flatter than it should (if you're trying to go for a realistic look).

if that's the case, we wouldn't see it. :P

If you listen closely, you can hear the sound of me being very confused and unsure how to apply this information to my art.

Sorry I wasn't clear: An apple or cherry has a very shiny surface, so with only a well-placed reflection of light source, you can give a very realistic sense of volume. You can even go as intense as white color for this reflection spot.

But you can't apply this technique for a peach because it won't look right : the peach skin is fuzzy and doesn't allow such intense reflection spot. (If you look at a well-lit peach you will see the light spot reflection, bt only at the tips of the "hair", it's so subtle that you can't really represent it in low-resolution pixel-art)

Now the trick is to manage to draw the kind of two-color aspect of a peach, without looking like a failed attempt as shading.
I looked at a few references, a consistent pattern is that a peach always stays yellowish near the stem (and leaf).