The game feels pretty good, the controls are responsive and the UI is well made. I played one full run with the starting character and it felt very easy, I wasn't at risk of dying at any point. Maybe I was just smart/lucky with my build, I dunno. I was admittedly a little bored by the end of the run, but that might just be because I'm not much of a VS-like lover. I then tried out the two other characters for a bit, but I didn't play full runs with either.
The game sprites are very charming and all look cohesive together. That being said, I'm not a fan of the the VFX: they don't match the game's art style at all. I would try doing something closer to your hand-drawn sprites, the default-Unity-looking explosions and trails are kinda soulless. On that note, the post-processing effects like chromatic aberration and bloom don't fit in too well either. The environment could use a little more visual interest as well, and as others have mentioned, the sound design leaves a lot to be desired.
I would often get the wrong description when hovering over an upgrade, and sometimes the description wouldn't update at all when I hovered over to another icon. That was the only bug I noticed.
The game looks promising overall, I have no doubts you can polish it more and end up with a very fun product. :)