Ask “What do you want?” and then work back from the answer.
For example: If you want to run a 5k, in under 20 minutes, what would it take to run a 1k in under 4 minutes? Or 5k in 30 minutes then 25 minutes before running it in 20 minutes. The maths is simple enough.
However, is it the customer’s job to know what they want? Steve Jobs famously said “No!” If the end in mind is “Where can we take the customer?” “What experience are looking to create?” That’s less about feedback and more about how you make the customer feel.
How are they using and working with the product?
“What do want?” is a great coaching question, but it might not be such a great feedback question.