Well, that is one way to look at it. Another way is to suggest the book probably would not have been printed, and certainly not in such a large volume had it not been written by an already well known author. There are quite a great number of books left unpublished of equal or greater quality that just couldn't get the presses to print them. The fact that she had such a great chance to publish again after Potter is already a somewhat large privilege in the cutthroat world of publishing.
As for this new read - without the fame machine behind it, a modest sale of 1500 copies is not surprising (her agent also knew who she was, as to probably how she secured the printing in the first place, given how hard it is to break into a market). Though we can expect now the mass printing that will bring this new one to best seller.
Fame is a double-edged sword. If she didn't like criticism she should have published a different novel or not published at all. As it is, she is sitting on a pile of gold, and still makes good money from book sales - her kids are going to be quite well-off, as probably will her grandchildren, etc. so there is no lack of personal achievement there. She can I guess just put writing as a sort of hobby and write the books that she wants, regardless of a public opinion against her. After all, the Ivory Tower did not like Potter as much as other favorites in the first place. Literary fiction is far more dangerous a field, as lack of proper style in prose cannot be dismissed with "well the book was just written for kids, so of course it is simple." As far as I am concerned, she uses far too many adverbs (almost on every sentence) which is a mark of amateurish writing (in the sense that she cannot convey attitudes or the implied meaning of the adverb through the basic narration or tone of dialog). We call such writing redundant in literary fiction, but we let it slip with Potter because the books are cute. When it comes to books for adults though we are far more picky. Such an angle of judgment is of course biased against children's literature, and not one I would hold to myself (as I am dismissive of almost all of Rowling's work in general) however seems to be the dominant train of thought amongst critics of her work.

