Alrighty, here come some reasonable suggestions:
An ability to skip/reroll the upgrades. I've tried to go for a "Level 10 without picking up weapons" challenge and the game bricked me with a level up with all options being weapons.
Maybe an ability to choose a starting weapon? If it's a "Vampire Survivors but with cars", the builds are very important, and what's the biggest contribution to the build if not your weapon?
It seems that your car, after hitting an enemy car, gets immunity frames. It would be more readable if they were shown with a car model "blinking"/flashing/pulsating/whatever is the word, you get the idea. Also, it looks like you can hit two cars in a row which is... cheesy?
Speaking of hitting cars, whenever you hit an enemy car, it, for some reason, destroys, yet your car just takes damage. I think it would be more engaging for your car to also deal retaliatory damage to cars and not just straight up pop them out of existence, as it would make people think about tank builds where you're not just a shell carrying weapons but also a weapon yourself. Not only that, but it also would make your efforts of killing a single enemy not flush away just because you hit that enemy and it didn't drop any sweet gold.
There's a curse that gives a chance for a giant variant of enemy to spawn. It, of course, has a downside of enemy having more HP... but dropping the same amount of gold which is a bit unrewarding. Making them drop a slight bit more gold would make them a high risk high reward enemies.
It would be a good quality of life change to see what curses you've picked up. Just a small thought.
If anything - I'll add more in the replies