But it's far from true.
Sweelinck combined English figurative writing with Italian counterpoint techniques. Bach used polyphony to the highest degree in his writing. Mozart was famous for beautiful and elegant melodies juxtaposed with various kinds of accompanimental figures, Brahms and Wagner - for their seemingly endless melodies. Franck embraced the chromatic harmony which led into a new era of French symphonic school. Durufle was a modal genius par excellence. Messiaen took up the ancient Hindu rhythmic system and created a highly authentic style. The list goes on and on.
The thing is that none of these achievements happened in a vacuum. Every one of these masters kept their eyes open and learned from a wide variety of sources.
And what about you? Do you also want to learn from the masters?
Steal their techniques and combine them into a new whole.
That's how you become original.