Hi ! Thanks for the detailed feedback !
I wanted do have waves at some point but couldn't do it in time sadly. The real goal is to have several maps, with more interesting layouts and stuff. Right now, for performance and pathfinding concerns, I can't do anything too fancy without having zombies hug walls :D
Concerning the incentives, I thought exactly that ! I added two ranged enemies : Necromancers, who spawn enemies from the edges of the map, and the rangers who shoot green projectiles that can only be destroyed through collision with the player.
I wanted to do more, but doing this solo was really, really intense ! At least I have lots of ideas for later :)