It would be of best way to improve your map building skills is by looking at tutorials, playing skirmish maps, and understand the functions, doodads, and atmosphere of each map's theme.
This one is just an expendable to your previous altered melee map, you only removed the custom materials but the map's functionality is still there which is bad and needs dire work to be given a approval feedback.
Little tip, try to compare your map with one of blizzard's 4 player maps, trust me it enhance my visualization in mapping.