It’s an old tripe. Good artists borrow, great artists steal. But there’s more to it than that. You’re moving into a realm now where there is a passing down of ideas. Lyrical themes, chord structures, melodies, patterns, styles. It’s all part of a grand tradition. Think about the blues. It’s just 3 chords. The same 3 chords. Everybody is playing the same 3 chords from Howlin’ Wolf to BB King To Eric Clapton. What it boils down to is style. How will you personally express those time-weathered ideas? Use them, distort them, rearrange them, mutilate them, or just plain interpret them with your own unique ability and perspective. It’s like Dylan said, the old songs give you the code for everything that’s fair game, and everything that belongs to everyone.