As someone who still listens to Cream discs on a regular basis, I believe that the energy of youth and the influence a Jack Bruce's genius were responsible from the great music they created together. Derek and the Dominos, which I know note for note, is still very enjoyable but not what I'd call transcendent like much of Cream's material was.
Like Paul McCartney, most of his output since then has been boring, and sometimes vapid. (Tears in Heaven)