Battlefields are supposed to be plain most of the times. "Black Battlefield" is a good example, but lacks care at many points.
We are standing in a field with almost no trees, some scattered resources and few rocky areas. This is a battlefield, but it does not provide some basic enhancement for players to survive. They must make it with no wastes and, if lucky, cut some trees far too distant from their base.
Visual Appeal: 2
The main theme is weird, this explains the low beauty of the map. Distant and deserty areas with some resources and no life. There is some kind of separation with the terrain, but it's not pleasing. Plus, the trees been far away: We can imagine the whole map as a random one with less objects in it.
The difficult management and the distant trees drop playability a lot. Players must rely on the next-to-them resources and send many villagers cutting woods, else they will be very vulnerable and less developed. The standard AI can not succeed here at any means. In general, playability does not follow the game's intention.
"Black Battlefield" is mostly recommended to present some theme/idea, but can not support gaming. There's no need to come up with a never-seen-before theme, unless it can provide more to the "audience".
Rating is low not due to discrimination, but due to the effort that did not go as well as supposed to. You can check others' works (especially the high-rated) and do your best.