Not trying to brag here, but I have actually directly collaborated with a former television writer who taught me (and our other mutual collaborators, of which there were several) about the general established functions of a television writing room and about the hours and hours of work that individual writers put in to bring a television series to life.
Through my collaboration with the above individual and our other collaborators, I also learned firsthand about the difficulties, complexities, and subtleties involved in specifically adapting something from one medium to another.
Other people might trot out the "complainers don't understand" argument, but when I do it, I do so based on my own personal knowledge and experiences.