And of course here are some of my thoughts on his post:
This is of course very true and wise-words for any writer to keep in mind. Just look at such books as Twilight, that while generally decent, are lamented as horrible by many and yet they have been extremely commercially successful. Then there is Harry Potter; again extremely successful, but there are still many that think it is teaching Wicca and abhor it.In closing, tastes differ. If you really want to be a writer, then write what you want, make it the best it can be (que the Army music), and keep seeking your break. Just make sure you can pay the bills in the meantime.
I have only just sent out my first submission to a fantasy magazine for a short story so I am sure I will only begin to realize the fullness of this point very soon. I can hope that my sub will be accepted, but F&SF is very picky and they have the ability to be with their large following.
On the other side of the coin, there will be some aspiring authors that write poorly with ill-conceived derivative plots that will also (given some persistence and luck) find someone to publish their work. Granted that there will be very few (hopefully) that can maintain this charade, it will and does happen. Just look at Hollywood and some absolutely horrible movies where millions were spent on pieces that were hardly worthy the cost of their celluloid.
In regards to your story, perhaps your teacher was greatly distasteful of genre fiction and felt you had potential and were wasting it on "drivel". Perhaps it was his strange attempt at caring and supporting you in your writing.