By your definition, why isn't Star Wars and SF scifi? If we had interstellar spacecraft (technology) we would likely have the impact and intrigue displayed by the empire and republic, of different worlds interacting as they do in SW.
I would define Space Operas (my favorite are by Alistair Reynolds) Space Westerns (SW) and SF (Star Trek) as all genres of scifi.
SciFi is just fiction with lot's-o-science.
Well no. Because Star Wars isn't a story about technology or science. It's about good vs evil. Just because it's in space doesn't mean it's automatically Sci Fi. But that just enforces what i was trying to say before about old school and new school Sci Fi. You are obviously new school
In my opinion old school Sci Fi uses technology/science as the foundation of the story whereas new school the technology/science aspect is not a part of the story it is just put in there for no obvious reason except that it looks good.
SF in my opinion is where they imagine a certain type of technology/science and visualise it in a future setting where it is prevailent in society. An example of SF would be Steampunk. A society where everything is run by steam. This is my favourite genre in SF. But i also like Clockpunk. An example of Steampunk is Wild Wild West with Will Smith. Other examples of SF include Metropolis and maybe Astroboy. I don't understand how Star Wars is SF or Sci Fi but people just called it that.
But i do agree that it can be hard to identify genres because they overlap so much...