I find it puzzling and sad that anyone cares what gallery owners think of their work. Now, when I say "cares," I mean it in the sense of them critiquing or advising any given photographer with regards to how and what they should be shooting. That should not be their job. Their job is to know the photo market, what customers and museums are looking for and how to sell and promote a photographer's work. I know people have differing opinions on this matter, but I believe that photographers should know how to take photos and galleries should know how to sell them. If a certain gallery can't sell what you love to shoot, find a different gallery. Don't change what you shoot.
I often read or hear about photographers that are upset or confused by gallery owners telling them how they should change their work to fit into the current market or to increase sales. It's putting the cart before the horse. First, you become an evolved and consummate photographer, with a personal style and opinion. Then, if it's your desire, you seek out a gallery to represent you. A gallery is a store. It may be a wonderful store that shows people your work at exhibitions and openings, but it's a store just the same. They need to move product to stay in business and that's the way it should be.
I think if you're gonna be a commercial photographer, then get jobs doing just that. You'll probably make more money than in a gallery and it wont get personal. If you're gonna shoot what you love, then don't ask a store owner, the gallery, what they think about your work, other than to see if they would be interested in selling it. It would be like a clothing designer asking a local store owner what they should design. They only reason for that would be to see what sells. Do you really want to be represented by a gallery where your purpose or motivation to produce work is to sell it? I know I wouldn't.
I've said it before and I suppose I'm saying it again. Too many emerging photographers that I speak with want to make books and be in shows before they have established a strong group of photographs. It takes time to mature in any of the arts. Don't rush it, give yourself 7-10 years to let things evolve. This is a lifelong journey that will reward you many times over. It can not be rushed.
It didn't used to be like this and I think in many ways its a sad state of affairs. It's a good thing that photographers like August Sander, Lewis Hine, JH Lartigue and Robert Frank weren't concerned with what a gallery could or couldn't sell when they were creating their remarkable photographs.