It’s a nice game, and with good execution it has potential. Maybe the driving difficulty curve is a bit steep at first impression, although it’s true that by the second lap it already feels much better to drive. Still, that might make some players drop it at the beginning, even though personally I find it rewarding.
Adding NPCs would be a big step forward, but without getting too deep into that just yet. Instead, you could implement a more dynamic movement system using Bézier curves or Catmull-Rom splines (I’m not entirely sure of the exact name in your engine), or even improve the system with waypoints so the movement doesn’t feel so static. If well tested, that could give a much more natural result.
A while ago I prototyped an autonomous vehicle locomotion system, and what gave the most realistic result was precisely that approach: smooth routes with control points. I’ll leave the example here:
https://www.youtube.com/watch?v=h9yWlw6ydv8
Overall, the game is in a very good state. Even with just three maps, a bit of progression system, and NPCs, it would already work well.
Finally, I wonder if you’ve considered changing the design of those areas where you have the “safety reinforcements” on the curves. Instead of punishing the player, you could let them use them as a help or even a driving advantage.
