Answer is pretty simple... You probably updated your monitor since last time. The spawnrate of the enemies is tied to the refresh rate of your monitor :/ That is why it is so much harder. And yes that is the most stupid way of doing that. I have no clue why the developer did that.
Damn... Know anyway to downgrade my monitor's refresh rate? lmao, thanks for the reply though, I'd honestly completely forgotten about both my comment and this game lmfao