I think all book purists and ardent lovers of Shelley's novel who are jumping on GDT's Frankenstein movie and are raging against it already because it's different from the novel need to take several things into account:
GDT is a big fan of monsters. He loves monsters. He takes monsters' side over humans all the time or most of the time.
In his movies monsters are often complex and sympathetic, while the humans are the real monsters.
GDT personally made fix-it fanfic movie Shape of Water based on Creature from the Black Lagoon where fish monster and main female character had romance and ended up together.
At one point during promotion of his Frankenstein GDT said that his fave Dracula adaptation is Coppola's Dracula. Yes, he read the novel. No, the differences don't matter to him.
Because GDT doesn't care about book purism and book fidelity or book canon in general. Here's what he also said while promoting his Frankenstein: "What I find beautiful is that when you create a universal myth, whether it's Frankenstein, Pinocchio, Dracula, or Sherlock Holmes, the myth itself rises so far above the original material that any interpretation is equally faithful if done with sincerity, power, and personality. If you think in terms of fidelity to the canon, you would be completely paralyzed."
Now, taking into account points 1-5 here's a very simple message and conclusion: GDT has never been a person you should or can expect perfectly faithful adaptation of Mary Shelley's novel from. He was never a guy for this job. He was always going to make his very own take with his very own brand of approach. Yes, with extra villainous Victor, yes, with uber sympathetic Creature, yes, with some Elizabeth and Creature romance, yes, with everything else he cut, changed and all that.
So instead of jumping on GDT or his movie you can either approach it as its own thing and vibe with it, or if you can't manage to do that then really, you still have Shelley's novel, nobody's taking it from you, just reread it, watch other adaptations of it, like that ballet or the Hallmark miniseries.