nouripen
Tech is a tool. In our society, tools have owners, wielders and people who commission their making. Tools are designed to have certain benefits and limitations; purposes they amplify and dampen. (For example, DRM is designed to dampen the ability to copy without permission.)
Later, you define tech as "human capability of solving problems and adapting environments". To that, we can add, "And in particular, the constraints we put on that capability." Tech is a massively collaborative venture (from children who mine raw materials, to societies that fund a certain kind of tech and not others). Therefore it's social. Absent "an exponential improvement" in social organization, "an exponential improvement in technology" may just amplify dystopian impulses.
“Final Working Definition: a bullshit job is a form of paid employment that is so completely pointless, unnecessary, or pernicious that even the employee cannot justify its existence even though, as part of the conditions of employment, the employee feels obliged to pretend that this is not the case.”
“The attentive reader may have noticed one remaining ambiguity. The definition is mainly subjective.”
Then goes on to explain that many cases are obvious: like if an office worker's spending 80% of her time making cat memes. But even in more complicated cases, you're likeliest to know best. (Not managers. The higher up you are, the more people have reasons to hide things from you.) After a couple years at the same company, normally people will learn enough of the company's secrets.
The OP asks a key question: "In an efficient market, why would profit-focused companies employ a bunch of people who by their own admission aren’t doing anything valuable?"
Anyone wondering this should skim the book, which squarely addresses this concern: "This is always represented as exactly what would never happen under capitalism. The last thing a private firm, competing with other private firms, would do is to hire people it doesn’t actually need. If anything, the usual complaint about capitalism is that it’s too efficient, with private workplaces endlessly hounding employees with constant speed-ups, quotas, and surveillance."
Don't know if I should spoil the explanations. :)