I think you should gradually increase the difficulty. The first spikes might be slightly too difficult for many people.
Also, the regular enemies(first one you encounter) might be too strong as well. It takes 3 hits to kill iirc? I just started ignoring them after a few tries. Maybe have different variantions of them, with different colouring? The first 1-2 you encounter should be rather easy to get rid of. Then you can make them stronger, requiring more hits to kill. The problem is that I don't know how long the game is, so I could be wrong about this.
About the visuals, I wouldn't say they are good or bad. Just simple visuals that work for a game jam. I can see the boss fight from the gif, that looks ok.
Would I buy such a game? Most likely not. Not my cup of tea. There isn't anything special about it, but that's the thing about platformers such as this, it's very hard to make something unique. It's the genre itself.
I hope this harsh feedback helps.
Best of luck,
Remi