From an editorial standpoint, Twilight is awful.
The book itself is on par with any other disposable romance novel. Plenty of Harlequin romance novels are as bad as Twilight. Hell, Meyer originally wrote Twilight as a Harlequin romance novel. It shows, and Meyer is about on par with most awful corset ripper authors, which is why none of her non-Twilight books sold.
The innovation was that it was aimed at teenage girls rather than middle aged women, and made a gigantic pile of money doing so. Like the kind of profit margins most publishers would stab their own mothers for, we're talking hundreds of millions here. So of course, every other publisher starts cranking out awful Harlequin level YA novels written by authors who couldn't hack it writing fanfiction.
You can literally trace the worst trends on modern speculative fiction especially all to either Twilight or Harry Potter. So the hate is justified. And the only reason some of the critics of it a decade ago are pretending its not is because CURRENT YEAR POLITICS means saying literally anything written by a woman is awful is sexist/fascist/literally Gamergate. That and I suspect many of them, Ellis included, realize they're as awful at writing as Meyer is.
That people hate Twilight isn't just because it's bad, but because it was massively successful, and directly led to hordes of imitators that were often worse, and dragged down much of the surrounding genre with it. AKA the Nickelback effect, that Nickelback sucks so badly they more or less killed rock and roll's presence in popular music.