This is true, but to a point....
Art buyers, art directors, editors and curators are just like you and me, the like to be wowed and they like to see independent thinkers. In some ways, if you have to ask your customer what they want, then you are simply not what they are looking for in the first place. For example, some photographers sell work or get hired based on what they can do for the client and how they fit into the overall team driven perspective, I have two clients that I have had for over 10 years that are like that, we are a family, we know what needs to get done and no one is a prima-donna about it.
But then there are photographers who's work sells or they get commissioned simply because of who they are as an artist, they have staying power, they have a distinct identity that is beholden to no one....they are often one of the most if not the most successful in their genre.
I could not have expressed that view any better myself. In short: the cream rises to the top.
The perceptions you cite about market demand and trends are perhaps the number one reason I am getting out of commercial work and doing strictly fine art...I don't want to show people what they want to see, I want to show them what they have never seen before.
You've undermined your first point somewhat with this last part, which suggests that success in commercial photography requires that you play the conformity game. As you stated so well, it's the independent thinkers who reap the greatest rewards. Moreover, it's important to keep in mind that fine art photography works the same way. There are fine art photographers who kowtow to market demand and trends, and then there are those who are setting those trends. The latter group is of course most likely to enjoy the greatest success.