Hmm... it looks good to me; I'm not quite sure what you mean by the stitches looking undefined/separated. Have you tried using a different colour of thread and/or fabric? Sometimes colour affects how we perceive the look of a stitch.
I do have a couple other thoughts:
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I noticed a bit of puckering in area A. That might be due (in part) to your stitch length being too long. It looks like it's around 3.5 right now; I would shorten it to 2-2.5.
There are a couple places where the line of stitching doesn't look perfectly straight (stitches look "angled"). I've marked these B. This is normal, and doesn't affect the actual straightness or strength at all. It is a result of the thickness of the thread relative to the fabric; when the thread is too thick for the fabric, the stitches develop a "misaligned" look. This is because there isn't room for the thick top and bobbin threads to lock completely within a thin fabric. You only have a couple places like this, indicating that your thread is a good match for the weight of the fabric.
You might also try tightening your tension very slightly, both top and bottom. Your stitches look balanced, but since you're using a fairly thin thread the stitches can be a bit loose at the default tension. The stitches will look more like ( than like | if the tension is too low, which it might be since you're using relatively fine thread. Start by tightening the top tension (a very little bit), and see if you think it looks better. If you like the look, but the bobbin thread starts showing through, tighten your bobbin case tension (very, very slightly). You probably won't have to do much bobbin adjustment, but the top adjustment might make it look better to you.
If you could describe more what you don't like about the stitch, someone could probably give more advice.