Science fiction is an extremely broad category. I have just read the concluding section of Prince Of Outcasts by SM Stirling. Soldiers fight with swords and the supernatural is manifested so is this sf? Yes. The story is set in the future. The premise of the series is that advanced technology has stopped working, therefore warfare has returned to swords. The supernatural is a transcosmic consciousness that had emerged from a previous cosmos and has caused the Change. Thus, every feature of the plot is scientifically rationalized although several volumes read like fantasy. The companion series, about the temporally displaced Nantucket, is time travel sf without any supernatural manifestations beyond the as yet unexplained Change/Event. The premise of divergent timelines allows for any number of coexisting scenarios as demonstrated in other novels and series by Stirling. Sf as a literary ghetto developed various stereotypes and cliches but is always able to transcend them.