As someone who has lost to a child on national television;

https://www.youtube.com/watch?v=YL5GE6S7LEk

I can sympathise with the author of the article. The cruel truth is that it is very difficult to improve as an adult. I think the analogy to learning language is a good one - to get really good learn as a child.

As far as I know there are no instances of a player learning to play as an adult and reaching grandmaster status. Akiba Rubinstein, an all time great who didn't learn until 16, was (nearly) an exception. Another famous (almost) counter-example is one of the pioneers of the Russian school of chess who learned chess from scratch twice - the second time as an adult after suffering total memory loss from a war injury. Unfortunately my Google Fu is failing me and I can't summon any confirmation or recall his name.