However. . . .
Sometimes that's where the real creativity sets in.
Suppose someone tried to rip off Star Wars for a planetary romance. Some parts would be easy: change all the spaceships to airships, or perhaps some sea ships. Turn the desert world into a just plain desert. Turn the ice world into the arctic regions. Etc.
But how to rip off the time Han fakes jumping into hyperspace to escape?
With extreme difficulty, that's how. Probably do you good, if you ripped off Star Wars that closely, to devise some way around it.
But even incidents could be difficult. If you are doing a high fantasy that rips off incidents in a thriller, you may need to substitute something for the airplane a character uses -- even if you rip off only two incidents, they may have to be far apart in space but close in time.
It doesn't even have to be ability. There's culture, too. Ripping off an incident where a man and a woman meet -- except, hmm, in this society there's the matter that they haven't been properly introduced. And she's going to look very forward, speaking that boldly, which she wouldn't do. In the story setting it was ripped off from, she was merely bright and friendly, but then, they didn't care about proper introductions.
Easier if it was the original idea. That way you can build the world around the notion, so you have everything you absolutely need for the story idea you pry loose. Trying to fit a bright idea into an existing setting can really force hard work.