In other words, why is one particular abstraction (e.g. Javscript, or the web browser) ok, but another abstraction (e.g. React) not? This attitude doesn't make sense to me.
As far as x86, the 8086 (1978) through the Pentium (1993) used microcode. The Pentium Pro (1995) introduced an out-of-order, speculative architecture with micro-ops instead of microcode. Micro-ops are kind of like microcode, but different. With microcode, the CPU executes an instruction by sequentially running a microcode routine, made up of strange micro-instructions. With micro-ops, an instruction is broken up into "RISC-like" micro-ops, which are tossed into the out-of-order engine, which runs the micro-ops in whatever order it wants, sorting things out at the end so you get the right answer. Thus, micro-ops provide a whole new layer of abstraction, since you don't know what the processor is doing.
My personal view is that if you're running C code on a non-superscalar processor, the abstractions are fairly transparent; the CPU is doing what you tell it to. But once you get to C++ or a processor with speculative execution, one loses sight of what's really going on under the abstractions.
I've read the react source, and some of v8. Imagine how you'd implement hooks, you're probably not too far away. It's messier than you'd hope, but that's kind of the point of an abstraction anyway. It's really not magic, I really dislike that term when all you're doing is building on something that is pretty easy to read and understand. v8 on the other hand is much harder, although I will say I found the code better organised and explained than React.
If this is true, why have more than one abstraction?
If you “don’t like magic”, you can’t use a compiler.
Reading comprehension is not magic.
Yeah, JavaScript is an illusion (to be exact, a concept). But it’s the one that we accept as fundamental. People need fundamentals to rely upon.
Sure you can, why can't you? Even if it's deprecated in 20 years, you can still run it and use it, fork it even to expand upon it, because it's still JS at the end of the day, which based on your earlier statement you can code for life with.
I’d rather make comparative statements, like “JavaScript is more fundamental than React,” which is obviously true. And then we can all just find the level of abstraction that works for us, instead of fighting over what technology is “fundamental.”