Well i admit there's a limit on what can be done with a short small sensitive joystick yeah. I feel they did an admirable job for a realistic style game with a complex thing to control such as a bike and rider with a joystick, but it be alot smoother with a wheel let's say. I tried it with driveclub bikes, works well even though its not suited for it cause it's so arcade. Plus you don't have to use ur right thumb to control many things at the same time,since u can use the pedals too. It seems silly but if you set the wheel lock to a small degree it simulates a little how u move in a bike even, like leaning when turning. Plus you would feel the bike better in your hands like a physical thing, could have ffb for it too. I dont know why they don't support it, maybe its just because it's not worth it for them.
You can try upgrade the steering so you can adjust for longer rake and trail in the setups. It should make the turning less sensitive if works as should. But i think only some bikes allow that. Also some bikes are much easier than others even if they are more sporty.
Also if you use the helmet view it feels less twitchy when you tuck-in, and you have better control in turns, but it is harder to see the whole track in corners tucked-in.