For what it's worth, I watched the first of these a couple years ago when they first came out, and I've been waiting for the rest ever since. None of the one-page flexbox tutorials on the web really do the technology justice.
I was curious as well so took a look at the durations. This is over 2.5 hours of content. About a layout system. I have to agree with another commenter, either this is far too much content or what should be a pretty simple layout system is insanely complicated.
If you're unwilling to spend two and a half hours learning flexbox, you're asking for a bad time with CSS in general. The flexbox spec alone is about 18,000 words long, which is about an hour and a half reading time for most people, to say nothing of comprehension or grasping the nuanced details.
One could spend a lifetime learning the geometries of grid systems, so 2.5 hours seems pretty reasonable to me.
Except you haven't learned much after watching those two and a half hours. I would argue reading this [1] or this [2], while simultaneously mocking up a flexbox grid will give you at least the same amount of knowledge in much less time.
I generally agree that reading is a lot more efficient but some people have different learning styles and videos work a lot better for them.
There's also (bad) university lectures that are essentially just the textbook in lecture form without much extra benefit. I've always wondered why people bothered attending these since I'm a "book learner". I've had a couple of long talks on the topic and now understand that some people simply learn better with audio. Unfortunately for them it's less convenient than reading (time wise, quick reference etc.) but it's still good to have the option.
Lynda.com would be screwed if people knew they could just crack open some reference material instead of wasting away in front of friendly introductory videos where another human eases them into a new subject!
Creating a layout is not a simple problem, but implementing it is. The reason 'most applications suck' is more likely because of the designer (or lack thereof).
It's a lot, but it's mostly ordered by importance so if you only need to know the basics, you could easily watch the first few videos and be happy with that until you need the rest someday.
https://css-tricks.com/snippets/css/a-guide-to-flexbox/