As for the tutorial, it obviously didn't disappear, I just missed it.
I booted the game without a controller plugged in, it won't give me KBM prompts, even after pressing z x c, ctrl shift enter. I plugged the controller while in the tutorial and it wouldn't recognize inputs until I exited to level select with the mouse.
I replayed the tutorial levels so I now know about the boost. automatic is way easier to handle than the other modes already.
collisions are very weird. they either stop you entirely, throw you in the air, or even bounce you back with reverse velocity(not full power, the vector is dampened) The first guardrail in desert speedway even failed to act as collision once, letting me slip off the track when my drift was too fast(butt slid off)
the biggest enemy in desert speedway are the sign poles. I think you should remove their collisions or move the poles outside the track. I don't think narrowing down the track on the start checkpoint is necessary.
the way boost is implemented makes it less useful than it could be. outright ruining your play if you don't use it on a straight road. I wish you could use it in bursts, instead of all at once. I think it lets you exit drifts smoothly, so it'd by a really good tool that way.
camera tracking could be faster on normal play, but when you are on those tight curved roads like the green half pipe in the test level it absolutely has to be tighter, you can't see where you're going until you exit the bend.
My performance was way better with automatic but even if you removed the tight part in desert speedway it would still be a medium-high difficulty track imo. the reason being that it's somewhat easy to lose control by overcorrecting when exiting curves and the high speed of the car.
How to make easier tracks.. the faster the speed, the wider the road. I guess this would probably be it. I feel like it's the general rule in trackmania stadium. And casualize the steering a bit but I doubt you want to change steer feel at this point.