Why is Janeway's return from death not the stuff of science fiction? Do you not accept that David Mack's Caeliar were science fiction? You might not appreciate the "return from death" plot line, or like me hate the over use of "interesting and loved character death" as a plot line, but that doesn't mean Janeway's return isn't science fiction.
I'm not here to argue simple plot devices because it comes down to a matter of taste, but what makes up "science fiction" is pure speculation. It is all about world building and Star Trek is already in the division that uses "back from the dead plot lines," and they have been for years.
While I am sorry that you cannot appreciate "living" Janeway as much as a lot of us do, I am certainly very glad Kirsten Beyer brought her back and I think the way she did it is not only good science fiction, and good world building, but fits to standard Star Trek canon.
Great Sci-fi has always been the stuff of myth as well. Using the great storytelling devices of the centuries to weave a compelling tale that also has something to teach us. Trek has always been about teaching us something and I believe that Beyer has a lot to say and to teach us about humanity, death, faith and destiny in her latest book. This makes Janeway's death and resurrection something worth exploring. It also makes it something that fits perfectly with exploring the universe in all it's many facets, new life and all that. So I completely agree with you Brit.