If people only did what they should, then many acceptable actions would not get done. Art & leisure or posting here are optional: there’s no should there. It is a fallacy of modal logic to claim an action that is not one that should be done is an action that should not be done.

There’s no reason you should post here, yet you did. Does that mean you’re “devoid of any morals” & “lack the integrity expected of a contributing adult”?

Imitation & derivative works hardly rise to anything worth fussing over & losing total perspective. If you pay attention, all human creativity is derivative, nothing is truly original. Works build on & reference each other. Techniques get refined. It’s why we have genres. From the Epic of Gilgamesh & ancient mythology to modern storytelling, or the development of perspective in graphical works across time, there’s a clear process of imitation & development across all of it.