Thank you so much for playing, and thank you for the honest feedback!
I definitely think multiple enemies of different types would've helped. My original plan was to have bats or some kind of airborne enemy (since you can also farm XP really easily by upgrading jump a lot and hopping on top of buildings, so this would've stopped that) but it turns out that hand-drawing like 20 sprites took much longer than anticipated, and it took a long time to figure out a probably super inefficient and convoluted way to billboard them based on the players viewpoint. I did some thinking on this post-jam and realized I probably could've just drawn it in greyscale and used a shader to make projectile enemies/different enemy types. That shader could've also tinted them red or something to show their approximate health too. Next time!
To go with the "All you can do is kill" feel, I had considered a "bloodlust" mechanic that would drain your health if you went too long without killing any enemies, but was afraid it'd be too annoying. Do you think something like that would've helped?