I liked it a lot! It's a really original concept and I would like to see more to that game!
The problem I had was that you can only push the enemies once they're dead - meaning if they are next to the wall you cannot move them out ever again.
Additionally I'd suggest adding the navigation nodes to the tilemap in order for enemies to just find the way to the player (can be done with a *soon deprecated* Navigation2D or Navigation2DServer)