That’s everyone’s say: “The customer first, know your customer“.
That’s true, but … how much is it true?
Knowing the customer without knowing your project people is going to create bad results.
In a few words, first know yourself, then your customer.
Moreover, for whatever reasons, customers (at least some of them) are going to be different – team members tend to stay the same; in any case, the team is the same.
Therefore, if you are going too far in “The customer first” policy you are going to get bad results.
I would like to add: very often, the customer will tell you: “Why didn’t you tell me of the problems I were creating? If you had told me the truth, the project would be in a far better shape“