Anecdotally I'd say this isn't true. I'm 42, and in the last 5 years I've learned coding, welding and a few other things. When I look around at my friends, many of them have also been learning new things. One of my best friends, who has been doing rockshows and awards his whole life, has started writing a childrens book, and has just come out as transgendered so he's learning a lot about writing, how to do nails, walk in high heels, etc.

I might be biased because I'm lucky enough to have unusual, crazy and progressive friends, but I think learning new stuff has less to do with age, and more to do with social factors such as having kids (and thus not a lot of time), or having large monthly expenses due to cars, houses, etc.

These things are correlAted of course, but I don't think age per se is a factor.