* Out of all people, and especially in the newer generations, it is increasingly uncommon to find someone with a desktop or even a laptop.
* Out of them, very few decide to do anything with it besides checking mail, social media, the web or play games.
* Out of them, very few decide to learn a programming language.
* Out of them, very few decide to learn anything besides Javascript or maybe Python.
* Out of them, very few decide to learn anything besides Java/C#/C++, learn algorithms, or learn tools like Vim or Emacs.
* Out of them, very few decide to learn anything besides Rust/Go/Haskell/Lisp/Scheme or even Fortran.
* Out of them, very few decide to learn a language with an alien, symbolic notation that resembles a code golfing language, and which, too, requires them to possibly learn a completely new keyboard layout to type with proificiency.
Not trying to discredit APL's contributions to functional programming and the like, but from the letter, it is pretty obvious Djkstra had little respect for friction. Not saying that he's right to dismiss it outright, though.