If most writers' reputations are made, or at least begun, before the age of 40, then very few novelists put many runs on the scoreboard after 70. Arguably, they can even start to damage their reputations, as anguished fans concede that their idols have feet of clay.I think the argument McCrum is trying to make is that a lot of great authors have great first works, and after that pretty much everyone tanks. That perhaps "people run out of ideas eventually, especially after three decades as a writer."
I don't think an 80 year old is any more likely to write something terrible than a 20 year old (which is to say, most people's books are terrible regardless of age. Except for your novel, reader. That one is great. That guy you hate? His is terrible). Thoughts?