I fault the big box stores with their "Anyone can do it" advertising.
And people who are dumber than rocks, and don't want to even buy a book on the subject.
Some of the trades are complex, especially with the additional code rules that arrive each year.
I couldn't tell you what's what in the OP's photo. And I've been a designer.
That said, an intelligent person can read and learn the terminology, see how things are done, acquire the tools, and do a workmanlike job.
But unless he has an experienced mentor, he won't know the tips, tricks and shortcuts of the trade.
The single most important trait he needs, is to know the limits of his knowledge. But most people don't know what they don't know.
So, as in most things, a little knowledge is usually, but not always, a dangerous thing.
I wouldn't hesitate to tackle any residential construction task, most of them by myself. But some, like installing a furnace or AC, would require the assistance of a qualified guy, because I just don't have the requisite level of knowledge, tools or experience.
You see it right here on GJ. A guy who doesn't even know the terminology, or understand how a thing works. Or even worse, a guy who has the terms down, but then insists on doing things his way, even when it is pointed out that it isn't the right way.
And what drives me crazy, is when one of these guys starts giving advice in a thread, confusing the OP. It's hard enough, when you ask a question on here, because you just don't know, and you get a mix of contradictory advice, and have no way to sort it out.
I am very in favor of people asking questions though. How else will they learn.
Bill