His #1 focus was building cars that won races. He was clear about that. And people bought his car because they won races. Lamborghini made amazing cars... that did not win many races.
There are not many accounts of Enzo being a likeable person, or a great engineer, or even a particularly good business man. But it wasn't a "mistake" how he treated Ferruccio's ideas.
So, maybe the moral of the story is listen to your customers. But it could also be: don't compromise and you'll still do fine, and they will go out and make what they want.