This is also true. But it's a question of levels of abstraction. The skyscraper is built out of (in part) a plumbing system, the plumbing system is built (in part) out of pipes, and assembling pipes is like assembling Tinker Toys. Which is why we give a five-year-old aspiring plumber a set of Tinker Toys to learn with. [1]

But this is only a few years after the web was invented, and the average website is still sufficiently ad hoc that the Tinker Toy level is a lot more visible.

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[1] Break any human-designed system down far enough and you'll often arrive at something as simple as a Tinker Toy. Although, of course, Tinker Toys are not that simple, so this fact may not help as much as you'd think. And this is not true of all systems: In metallurgy, the "simple" parts are atoms, quantum mechanics is not like Tinker Toys, and even if it was nobody has experience with a Tinker Toy set containing 10^28 pieces.

"Actually, it's like maintaining a skyscraper built from steel, concrete and glass integrated with complex HVAC, plumbing, electrical and elevator systems."

Adding, "Designed by a committee. Of MC Escher fans."

Two different development processes, two different outcomes. And unlike other 'construction'-type businesses, in software we have many different development processes.