300 pages of filler could very well be the same message told 15 different times in 15 different format hoping that most people would gain that precious wisdom from at least one of them.
I see this as a common fallacy of hyperrational people
A couple of very capable people I know can hear the story of something that happened to someone, and they get glazed eyes and can only say "Huh?" Then I rephrase it as "Imagine you were _______ and then _____ happened and afterward you were _____" and they're like "Well why didn't you just say that?"
Or the exact opposite.
Or like me. Give me an anecdote about something and I'll "Huh, interesting." Tell me about the reason you found it interesting, and I'm way more interested and engaged. Relate it to an event in my own life and now you've got me. But don't ever try to frame it that way for my wife, she'll get bored after the first five words.
It's not the message, it's what the listener gets from it.
I begin to think that if you don't understand the advice, you simply don't need it _yet_.
"You'll read it again and understand it on a whole different level" or
"The people in your life are there because you need them now. Don't mourn the loss of an acquaintance, it's because you don't need their lesson anymore"
The article makes the point that the wisdom really does take much longer to communicate - a nugget of wisdom like ‘accept yourself’ seems trite when taken alone, but the examples (presumably filling the other 300 pages) are what makes the advice actually sink in.