In that post you quoted from I'm talking specifically about film and TV LaQueen, not about literature or spelling and grammar, which I can talk about if you like.
It's a well-established fact that early broadcast media audiences couldn't handle complicated plots, which is why many of us today struggle to understand why Charlie Chaplin was so popular, despite him being extremely skilled and sophisticated.
The first of the modern multiple-episode TV shows was a thing called Murder One in about 1995. People didn't believe that something on telly running over 20+ episodes with many characters and multiple plotlines would be a hit.
Yet it was fantastic and is really worth looking up. Honestly. It ran only for two seasons and the second was lame, but it spawned 24, Six Feet Under, Big Love, Picket Fences, The Sopranos, The Wire and many more that I've forgotten that we're so used to now that are mostly okay but sometimes sublime.
It really is a myth that people have dumbed down. How many people found out more about Roman culture and its empire from the hundreds of programmes and books prompted by Gladiator? Or Greek mythology after the film and comic book 300?
We choose what to consume from an ever-expanding entertainment market, which is an embarrassment of riches and to my mind can only be good. The Rubáiyát of Omar Khayyám is essentially entertainment, not an improving work. At least, I hope it is.
And yes, grimbletart I used 'which' when I should have used 'that'. That's why I don't like giving hostages to fortune on these threads but snigger when people do, as many have done. Of course, I'm far too polite to point that out.