Coming straight to conclusion good concept bad graphics.
First coming to its concept its concept is like every multiplayer base game but a little more minimalistic in that.
The guns are limited so are the base thus it is good for casual gaming but not more then that, due to this fact it quickly starts becoming boring.
Add to that bad 8bit graphics, similar characters, and 2d gaming it pulls the gaming experience down.
But user base due to minimal resource requirement is its biggest pick point.