Earlier quoted context omitted.
I never find it helpful when people say they aren't that different from each other. Sure there may be some similarities if you want to take an analytical view of the genres, but there's an awful lot of people who like one but not the other.
The problem is once you look at the definitions it's actually quite hard to exactly define what's Fantasy vs Sci-fi. It's more a venn diagram, than strictly separate genres and everyone has their own definition of which is which. So when someone likes one but not the other, it's hard to discuss books because what one person considers sci-fi, another may consider fantasy pretending to be sci-fi, thus the complaints of…
You could argue a lot of semantics but the majority of fantasy and sci fi books are not blending the two.