I've just spent far longer playing this than I had any right to XD
As others have mentioned, the only real thing to work on is the balancing - and even then I played for quite a while before I realised I hadn't even damaged the hero, so the fun is there either way. I also didn't realise on my own that you could upgrade your minions, and if it wasn't a jam game then a tiny tutorial is all I'd want added.
Controls are snappy, with good feedback on spawns (both visuals and sounds). Fits the theme perfectly, of course. Great gameplay loop where you want to spawn lots of enemies to overwhelm the hero, but that levels the hero up if they all die.
I have only managed to win when using the... ahem... cheat code... would be curious to know what the meta is when playing legit!
P.S I saw an earlier version posted on the discord so it was great seeing the final product!