2 things

one which is the least important i think it should have moved from one note to the other a little faster thats just opinion but you do need to add some lower voices its really bland and plain without them its ok to have parts of songs were there is no low voice but for a whole song to not have any low voices well thats just a bad decision unless your shooting for a specific feeling in which case the song should be more like an orchestral piece and have different movements and be much longer so that feeling isnt wasted