- exact reuse of a long-ish word sequence(s) without credits -> not cool.
- complete/partial reinterpretation of an already existing story in different words -> it's fine
- Traced/almost identical image/drawing/painting (with the intent to fool someone) -> not cool
- Visual imitation in style/content but different approach or usage -> it's fine
I think people are too attached by the novelty of something, sure if I write a bunch of words and you repeat them as yours, that's not cool. But if something I make inspires someone and they take it, reframe it, rephrase it or whatever, go ahead.
People adore Star Wars, which is an absolute one to one of a hero's journey, it still has value. Most modern fantasy are basically fanfics of Middle Earth, still good that they exist.
Imagine someone just spamming sequences of notes at random for their whole life, does it mean they own anything else made here afterwards +70/80/90... Years?