Which is not surprising, I guess, because it has that rare quality of great music: a feeling or sense in the listener that this melody has always existed, timeless and eternal, and only needed to be revealed at some point in its full and perfect form.
He woke up one morning in 1964 with the melody in his head and immediately got up to play it on piano so he wouldn’t forget it. He called it “Scrambled Eggs” just to have something to sing — the real words would come later.
https://youtu.be/PNhj_MYZ69o?si=I1Wu02YNEf8raCWs
McCartney’s legacy as a creator of deeply original music with wonderful melodies is clearly legendary — you could even make the case that he belongs in the Songwriters Hall of Fame twice, both for his Beatles era and then his Wings era. No arguments here.
But “Yesterday” is on another level, a rare height that few songwriters ever see let alone reach.