As too many fiction writers know, one of the most frustrating exercises is the search for an agent and/or publisher. Among the occasional rejection notes (in place of the non-response or printed forms), I've received two that said the reader didn't warm to my protagonist. There are two arguments in my favor: first, the whole point of the story is supposed to be how that character changes; second, I deliberately try not to set up my central characters as unflawed, but I attempt to show them as real people.
At last I've read a reviewer's comment that seems to grasp what's needed in a critic, whether one commenting after the book is published or someone who will decide whether it's worthy of publication. Geoffrey Wolff, who is a long-time professional reviewer, is quoted in The NY Times Book Review. He says he regrets that too few fiction writers are willing to write reviews. "A novelist knows how difficult it is to write even a flawed novel, whatever an unflawed novel may be." Some flaws, it seems to me, are evidence of that sought-after characteristic we were taught in school to call "verisimilitude." I consider that a requisite for a novelist. (Apologies to genre writers with other objectives in mind.)
I guess I'd add that it's too bad more agents and editors aren't endowed with the same knowledge, and thus might have the patience to read more than the customary first 50 pages.