On one hand, plausibly she could write stuff that would sell well because there's a lot of real crap that sells well--as @
Deoxyribo9 and @
NZPIEFACE point out. And I did actually try to read 50 Shades, because I like SM and potentially could have been very happy with an SM romance (Nana to Kaoru, for instance, is really good).
Oh my god it was such crap.
But I also agree with @
Panino -- there's actually some
really good stuff that isn't at all original. Morinaga Milk is one of my all time favourite mangaka and her stuff doesn't have a trace of originality, but her craftsmanship is so good and her stuff often has so much heart, that when she's at the top of her game she can bring a tear to my eye doing a scene I've seen a version of a thousand times. It's like when she does it I'm seeing it for the first time again, or remembering why this kind of plot line is popular in the first place. To be fair to Milk-sensei though, Hibiki said "This has no self-expression in it", which doesn't apply to Milk-sensei; her characters are always very much Morinaga Milk characters and her art can be very expressive. So I guess for something to be unoriginal and good, it still has to bring something of its own, something personal, like characters who are their own people or something.