Much like the other commenters, my view is that this movie is bilge. Really it's not much different than those sword and sorcery movies that were inspired by the Conan the Barbarian movies -- this is more like Conan the Destroyer than the infinitely superior first film.
There are so many flaws, and they have been mentioned in detail in other comments, they can't all be listed, it would use up the word maximum.
Suffice it to say that this is in the area of "Ator the Fighting Eagle" style flicks, very low budget, no talent to speak of in the direction or cast, and the writing is atrocious.
It is too bad, it appears the makers figured they could make the same movie, with the silly comic relief, that they've made dozens of times before, slap the "Gor" name on it, and people would watch it if they were into the books.
The Gor books do merit a movie, and the makers wouldn't even need too large a budget, though it would help since the world Norman created is quite intricate. And yes, the sexual aspect can be pretty adult in the books, the latter ones anyway. But the first few are pretty tame in that regard.
Still, a reasonably budgeted R-rated movie with a talented director (get Milius!) could have been made and would likely been successful.