Septentrion_P said:
So how about putting "could be better" as the reason or "Not our preference".
... We use "Not approved for 3 days" to make it clear that the post was given a chance, but no mod doing approvals saw fit to approve it. So it should be obvious that any such post "could be better".

If a post has only one fault leading to a deletion, it will normally stand out. You will probably see someone comment about it. And depending on how bad it is, the post may even be deleted instantly.

However, most posts that are deleted after 3 days have multiple minor faults. Nothing so severe that a mod would delete it on sight. But enough to prevent any mod from approving it.

Septentrion_P said:
I'm pretty sure these images would have been approved years ago. Before this was a visual novel site, it was an anime site. Sometime, shading would include more than two colors, and it was considered nice and not required.
Thankfully, our standards have improved! Unlike the early days of this site, we no longer allow endless versions of the same CG. And since post 200000, only about 8.5% of posts have been game CGs.

Game CGs are drawn professionally, but usually on a tight schedule/budget. They usually can't compare to what many artists can do by putting a lot of effort into a single image.