Zombie beach, please help!

This is not as much as a showcase but a cry for help.
I don't know why people uninstall my game. Please try and feedback.
What's this that you don't like about this game? Is it too laggy, too easy, too hard, too ugly, bad control, un-intuitive etc... ? I am at wit's end.

This is my first try at making game in Unity so ANY opinion is very much appreciated.

https://play.google.com/store/apps/details?id=vn.ts.zombie