ACC is more than just playable on a controller. It's super fun.
After messing around with the settings and tuning the basic things like steering ratio. I find the game to be a lot more welcoming on controller without any assists. With steer filter and steering assist in controller I was able to smooth out the steering and create sufficient room for me to work with the stick and not literally translate every input 1:1 like iRacing which is just atrocious.
Also they should rename steer assist and filter in controller settings to something mode appropriate. I had it disable for sometime think it was assists but all it does is smooths out your input based on your speed and keep the inputs consistent and linear.
No clue about competitive but its really sufficient to get started, learn and unnoticed your technique and be in the mid pack if not in the medute