Puccini used three Chinese traditional melodies in his Turandot opera. What makes a difference, is that he wrote "Turandot" around them.
Since ever composers take some other composer's theme to work upon. Famous cases:
Prokoviev: Rhapsody over a theme by Paganini (also known as Variations over a theme by Paganini);
Beethoven: Variations on a valzer di Diabelli (also known as Diabelli Variations);
Richard Strauss: Metamorphosen (which are variations over a theme of the Eroica symphony by Beethoven);
Mozart: Variations on the theme Je vous salue maman;
and very many others.
That is a creative effort, and it is art.
When you are in the conservatory, you are given a theme and you are asked to write a fugue on it as an exercise. Nothing to do with taking somebody else's photograph and applying some patches here and there.
In photography school nobody is given the assignement to "patch" somebody else's photograph because it is an exercise which has no merit and no sense. No creation whatsoever.
I bet Mozart and the others would be VERY pissed off if their work were compared to the "work" quoted by the OP.
You recognize shit because it looks like shit and smells like shit. Don't overthink about it or you might end up confusing it with ice cream Just trust your common sense.