I loved this game and I made it all the way to wave 4, but the only real problem I have with this game is the hitboxes. Make the player hitbox smaller so that the game can be more forgiving with the player.
I appreciate your feedback. The game is meant to be challenging, but I know it can be frustrating sometimes. If you haven't already, you could try the easy mode which will give you slightly extra health regen. It's just meant for players who want to enjoy the game without as much stress.