Cute! Love that you did the art yourself, and the goblin's walking animation is so silly in the best way imaginable. The theme and prerequisite aren't really present sadly, at least not in a clear way to me except for a big horde. Furthermore, it is indeed possible to stand at the edge of the grass and swipe continuously with no threat of being hit.
For some improvements I'd focus on giving a reason for the player to do this, are they competing for a high score? A multiplier? A set number of kills per round? I'd also focus on giving some more player feedback to actions, like having a sound play when they slash their sword, have some screenshake when they take damage, some particles when a goblin dies etc. there's some great sources to be found when you search for "game juice". It'd help make the game more satisfying intrinsically apart from something like a score.
Overall, there's stuff to be improved but the character art you made is really sweet and you should definitely keep it if you continue developing this game!