> The whole point of abstraction is to use it without understanding it.

No. No, that not "the whole point" of abstraction. To benefit from reasoning and describing problems on a suitable level of abstraction you certainly do need to understand your building blocks.

> don't go study quantum mechanics [...] when you are writing JavaScript.

No, that would be as just silly as to wait for a doctate in thermodynamics before cooking an egg, but please have a decent understanding of HTML and HTTP before you write javascript web apps professionally.

Re: abstraction. You need to understand interface, but "not understanding implementation" IS the point.

You gave an example of HTTP, so let's discuss that. Understanding of HTTP concepts is useful for web programming. Details of HTTP implementation mostly aren't. Studying HTTP/2's header compression or HTTP/3's forward error correction IS NOT necessary.

The point of abstraction is that you can use it without understanding what's behind it, not that you should. There are diminishing returns after couple of levels, but abstractions in general don't come from thin air, and it's a massively easier to use an abstraction if you have some understanding of a level or two below it. It gets even more important when an abstraction is buggy, leaky, incomplete, or imprecise.

So yeah, quantum mechanics may not help you much when writing JavaScript, but understanding of lower-level programming, of how memory and networks work, just might.

That “just enough to get by” mentality is dangerous. When I see somebody who has put together a monstrosity that they can’t get under control it’s always somebody who didn’t really understand what was going on “under the hood”.