So assume a worker that perfectly knows and likes their job, but doesn't care about the process "above" him. If you enjoy the process of tiling and you have some experience with tiling, you don't have to care about what kind of building/room you are working on. Somebody designed the room, somebody picked the right materials, somebody probably bought them and it's in the spec/design. You can just "tile away" and make a career out of it.
Similarly in software, if you care only about programming and languages and whatnot and not the product - it's all you need with the right team/org. You won't be a product owner and you wont advance to "decision-making" levels in the company, but if you don't want to why would you need to.
The issue I have with is the statement of "make a career out of it". I don't think you can, at least not in the software industry, a lot of folks are perfectly competent developers but can't move forward and eventually get replaced by younger/cheaper developers because they are basically doing the same thing for the past 10 years.
I agree with having passions for something, but making a career out of it is a lot harder if you don't do the "extra".
I'd argue that they are replaced (if they are, because I'm not sure, there are not a lot of old folk because IT industry is pretty young, I already worked with a few 50+ mid devs and the pay is kinda reverse, because old folk already have homes and don't need to pay off huge mortgages) not because they didn't get promoted (mid dev -> product owner / domain expert) but because they stopped upgrading the skills relevant to their current job.
So in terms of the example presented by the author it would be developers that are no longer even hyped about languages/tools. And in our imaginary "tiling specialist" it would be a guy that didn't care that the current fad is some kind of funky pattern + new material of tiles and still wanted to lay old ceramic square tiles for his entire life.
I'm still not convinced that there is a scenario where you __have to__ care about "the domain" / "the problem being solved" / "the bigger picture" that much. You can, it will improve some aspects of your career, but you don't have to and it would degrade other aspects of said career (we all have about 16h max productive hours daily, and I'm being generous).
Where most people are failed by those around them, like parents and school's is pointing out when you leave education, you wont stop learning, and its always good to ask questions and plan ahead what you want to do with your life.
Arguably have a bucket list which will change as you age in order to have something to aim for, and dont get caught in the trap of settling for second best or end up being used by people who think might be your friends but only knew you because of what you could do for them on the cheap.
Now you might have called your summer job slave labour, I look at it as being paid to exercise as well as learning new skills and make new contacts.
On the subject of aimless excited programmers, there's lots of ways to look at programming before learning a language.
If one wants to earn a lot of money, then consider database related programming, everything is data, even spreadsheets can be considered flat files of sorts. And whilst you probably wouldnt use javascript to write a database app in, even though you could stuff data into a cookie and run it client side, there are better general purpose languages suited to database work, besides the obvious sql languages.
If chasing the money, consider looking at what's involved in high frequency trading where you'll be writing your own OS to maintain the super high speeds required for algorithmic trading. Co-locating data centres as close as possible to trading exchanges is just one part of the problem. [1]
IF you want to do apps for smart phones, again look at the languages that deliver the most for you, but also consider whether you should go with a popular language like dotnet or java thats portable across platforms, or whether you want to go with a niche language that might become less popular over time especially when considering there are thousands of languages that exist, with many having fallen by the wayside.
[1] https://www.ted.com/talks/kevin_slavin_how_algorithms_shape_...