My wife and I just had two trips to AirBnBs and were trying to provide a review. We have a checklist but no opportunity for providing a free-style narrative. I don't understand, why? I just have the stars and what I found especially appealing. Then it goes to private feedback.
It goes to private feedback first, @Gary167, and then the final screen (at least for me) is the public written review. Did you get all the way to the end? I see you are a seasoned traveller, and unlikely to miss it, so if you are not seeing that final screen, you might want to give Airbnb a call.