Genre and style are definitely issues to overcome. As I said earlier, the story is genre-bending and hard to classify. A spy thriller, turns almost fantasy, which leads to sci-fi. Three distinct audiences but that is what came out of my head.
But giving up on 13 books seems like failure...
A couple of things come to mind.
You could re-release rewrites as a second edition, making it clear in the author notes that the stories have been substantially rewritten. Then either upload over the top, or unpublish the originals and replace with new books.
The genre changing is not really a big issue. Just the unexpected change is. What the first book needs in the sample is examples of all 3 genres, so the reader knows the book is going to cover all 3.
That means having some sort of interludes of space opera and fantasy showing up in the first 10%. Even if its a media report of a space ship and one of the characters commenting they really want to go to space one day. Just insert something in there that demonstrates that space is coming. Likewise the fantasy. Insert something as a forewarning.
You might put some readers off in the sample, but there are plenty of SO readers who like their fantasy and thriller as well.
Your problem is most likely that the people who mainly start are thriller readers, and then it morphs past their expectations.
What you want is to get it before Space Opera readers, who like some thriller in their SO. Then when it morphs, they're in their comfort zone.
To do that, the cover has to scream SO, not thriller, and the blurb has to show that SO and fantasy are coming.
Also, what categories did you choose? If the book is in Thriller cats, then try putting it in SO and Epic Fantasy instead.
SO readers are probably much more forgiving of genre hop than thriller ones are.