It's a good base and i'm so relieved I'm not the only one who noticed it: The economy needs to be reworked. I spent 33 seconds (11 clicks with 1 second cooldown to kill 3 snakes) to get 3 coins to gain 1% of attack. That's really really low.
What's most important is that the gameplay loop IS GOOD, you did a very good job with the game, the enemies, the UI, the small amount of upgrades, it's really suitable for a mobile game and I think it would even be a successful one, but you just need to improve the game's economy.
Check out Clicker Heroes and see how they did it, you get increasingly stronger monsters instead of nerfing the upgrades.
Still, you have a solid base, keep developing it, I'd definitely launch this on mobile, it could be a hit if you add more variety and balance the economy. Good job so far!!!