Did you actually get past the tutorial? There was a bug that spawned infinite enemies in the tutorial, and one that kept you from actually playing the game with enemy spawners and such. Can you please check again to see if it works? You can just press R to skip the tutorial. Thanks!
Viewing post in Chroma Slayer jam comments
I was able to skip during the lag and play the game on my first playthrough, but not the second (got stuck in the laggy part), so definitely good to deal with the bug. I just tested it now and it definitely looks like you've fixed the bug. No more extreme lag with the entire screen filled with enemies.