Sketching a Novel

For some reason I can't explain, I think about the process of creating my novel as if I were creating a painting. My previous drafts aren't drafts, so much as sketches of ideas. I've attempted three, maybe four depending on how you count it drafts of this story, and they've each been failures as drafts. I don't see much if any of the content of those drafts making its way into the final draft unless I sentimentally graft some in. On the other hand those sketches provided me with essential information. The first defined the characters for me. I knew by the end of that first brief draft who these people were. The second failure taught me how they did and didn't relate to each other. The third gave me the plot in a charcoal scribble. The fourth gave me a setting for the plot. This current draft is still just sketching. I'm exploring the vertebrae of this beast. I'm trying to make sure that the spinal cord is intact. I'm in no way ready to deal with muscles and skin. I'm still working in charcoal.
This doesn't bother me, but it's driving my writer's group crazy. "Where's the texture?" "This scene is taking place in a white room." "We don't even see this character in this scene." I tried this week to add in the extraneous details, but I found the work frustrating. Until I know what matters I have no idea if the scene on the page will even be in the final novel. For all I know as much as two-thirds of this draft will hit the floor in the next one. Why invest so much energy in what may be cut? Secondarily, I just don't have a feel for what details matter other than the conversations and interactions between certain key characters. I can't tell if it's better for the table cloth to be white like communion linens or some other color more emotive and descriptive, because I don't know if the tablecloth will be useful in conveying the final story. It may be that this entire scene will be rescheduled to a different time of year, or a different age, or even a different setting entirely. What good will all this gluing and pasting of detail be to me? Thirdly, they only give me four pages double-spaced every week. I'm already expecting this project to take between four and ten years. I've got to make time, and all that "texture" wastes valuable time.
I guess I can't expect them to see what I'm seeing from my charcoal sketches. After all I'm not Picasso.