Ali did not rematch Foreman, who was clearly the #1 contender between 1975 and 1977, and also probably avoided the rising Holmes
I don't know how anyone can accuse Ali of ducking anyone, even in the latter part of his career as champion. He beat Foreman more than convincingly, after which, Georges career declined between 75 and 77. I'm not so sure that a rematch was warranted. Holmes was a promising young prospect, but was pretty much an unknown entity until maybe late 1977. Up to this point, he was actually on Ali's payroll as a sparring partner. In the meantime, Ali was facing far more established contenders in Earnie Shavers, Jimmy Young, and of course Ken Norton. Rather than saying Ali ducked Holmes, it would be more appropriate to say that without the mentoring of Ali, Holmes never would have flourished. The fact that Muhammad Ali, was heavily involved in the making of another all time great, who would take his place in the grand scheme of boxing, is another big star on his legacy in my opinion.