The last paragraph may be true but not always.

David Krakauer has an excellent video explaining some of this, if I recall the GoldLab Symposium.

On the first, YouTube is an illusion. When our society advertises items like cooking shows, construction skills, it is responding to demand for those. This is fine, the skills spreading is good, but it is large error to think it follows this means the amount of knowledge is increasing. It's actually a signal of the opposite. We have lots of TV and YouTube videos concerning housing because they are becoming less accessible.

I strongly disagree elemental skills can be taught quickly. This is usually not true. If you go to a site and ask each trade how to do their thing they will give you answers in weeks and months, yet if you add them together it should take a person less than a year to be a competent builder. This is not true, something is wrong with this picture.

There is a conceit we have about some forms of knowledge, that we can easily reach them with formal descriptions. It actually takes decades to teach an apprentice the skills of a master, because real world experience must be carried out to be able to generalize. It is a serious error of epistemology that is common to the Western middle class. This only becomes obvious when you see people trying to do things. The worst part is we have measured information flow rates with different ways of teaching and the mentor apprentice system is literally 100 times faster than giving lectures to classes, this result is famous in education, it is called Bloom's 2 Sigma.

This is visible as you walk around Western cities, the old buildings have higher attention to ornate detail despite our extra power tools we have today the same detailing is too expensive to recreate.

The crux here is when we are very good at things we forget that they were hard at first. Then if the people don't transmit the information it isn't like formal knowledge where you can skate by with a description. Instead the next generation loses the skill and has to painfully relearn it. That is the paradox of 'elementary knowledge'.

You can lose information for thousands of years, that is what a Dark Age is. Things got cruder and cruder.

We have had some good overall centuries, but we can go backwards just like the Roman and Egyptian empires did. For Egypt the largest pyramids were built first, not last.