I think talk about "the impossibility of teaching well" is stretching things a bit. In my own experience, I had some philosophy professors who were phenomenally

I think talk about "the impossibility of teaching well" is stretching things a bit. In my own experience, I had some philosophy professors who were phenomenally great teachers and some others who were downright awful. Some of the difference might have come down to innate talent for teaching, but I'm quite sure that none of the difference was attributable to the amount of non-teaching duties they had. The best teachers I had were professors with heavy administrative and advisory duties, while the two worst had comparatively little non-teaching work to do. The main reason they were terrible teachers is because they just didn't give a shit; they were clearly just phoning it in.