This is a pretty creative and innovative game!
I can tell how much work and passion you put in. The concept of all the characters being vermin that are usually disliked is pretty great, it definitely helps the immersion. The gameplay is a little confusing for me, I think an in-depth but fairly short tutorial would help out a bunch. It's kind of hard to understand, at least right off the bat, what spells would be most advantageous for which vermin, but it is clear what they do and their effects.
I'm going to trust that the amount of content you put in is balanced, because the system seems rather fair to me from what I played. I would appreciate a simplified approach to things, for players that are relatively new to the genre like myself, but it isn't necessary for making the game more fun. Perhaps as the player starts off, they are rewarded for learning the basics of the game in the tutorial with satisfying victories; This can include fights against enemies that are really easy to beat. And this can be completely optional, for more seasoned players.
I also made my first game on itch, I could totally use your feedback on it: https://wasabiiii.itch.io/grass-elemental-demo-demo
I want more people to play this and enjoy it!