I actually enjoyed this one a lot despite the simple graphics. Maybe I can relate because my art also isn't too great haha.
The core gameplay loop is pretty funny and it's amusing to kick monsters off the ladders and watch them fall off the screen. The difficulty curve is also pretty nice and it gets very intense and frantic very quickly. I liked the music too, there's something charming about the game.
All I can really think to improve apart from the graphics is to add more enemy variety and maybe include some levels that progressively get harder as well as the endless mode.
This is a really nice entry and I had fun playing it. Good job! :)