One of the reasons is the lack of gameplay sound, having low levels of gameplay sound in your trailer massively helps, its one of the key aspects of any game, it would be interesting to see a video of it with the actual sound. Another thing is the particle effects appear a bit lackluster, this is reinforced by the height of the camera, the majority of your screen has not much going on. Not sure if it works in your case as you appear to have a camera that can be freely moved but minor screen shake. General things that give feedback to the players.
Maybe that isn't what the game is going for. But the high tempo of the music in the trailer sure makes it feel like it's meant to be. Here is an example of something that certain feels like every hit and move has a bit more impact.
