Thanks for trying it out!
Funny how the subject of your criticism was one of my main goals with this game - a spammable attack and a constant assault of new enemies, both are there to make the player play very risky and aggresively, I wanted this game to feel like Hotline Miami if it was a survival arena. I can see how not everyone enjoys it.
While mashing may seem brainless, you still have to consider your position afterwards, and also sometimes you have to actually time the attack to dodge something nasty. For me it looks like a classic Platinum Games approach - let the fresh players have satisfying successes, while leaving room for improvement by skill and understanding of the game.
There's 5 basic enemies and 2 bosses, and I've tried to make the enemy waves varied by mixing them up in interesting ways, in which they interact in some new, deadly way.