I disagree. The body of his work has changed no doubt, but he still has that magical sense to weave words into a melody. Even if only 5% of what he’s written is masterfull, in many ways above any other song writers, including the great American’s like Berlin, Porter, Rogers & Hammerstein etc. But to hear him he feels like he’s fallen short.
Dylan was (still is) the Yip Harburg of the 1960s, just as Paul Simon was (still is) the Hoagy Carmichael. To compare either Dylan or Simon to the above 1930s quartet--or sestet, if you were to include Gershwin, Kern, and Ellington, which you would have to, to complete the story--is to compare apples to oranges.
There are essentially two strains of American popular music of any intelligence: the music that glorifies American ideals, and the music that critically analyzes America in relation to its ideals. People like Berlin, Porter, Gershwin, and Ellington did the former--even Ellington's Black, Brown, and Beige ends on a literal and figurative high note. People like Harburg, Carmichael, Dylan, and Simon did the latter.
(With one exception, and that is how Carmichael slid into the role of patriotic tunester in WWII, which wasn't too difficult for him because he was a Republican who questioned FDR's policies, but who united as everyone else did after Pearl Harbor. It almost makes you wish Al Gore had been President on 9/11, because the Democrats would have supported his going to war, and the Republicans would have supported the country. Almost, because that's assuming he would have gone to war against the enemy the way FDR did.)