Returning to your original post,

We really are building things with too deep abstraction hierarchies causing knowledge to be divided

Abstraction is necessary, true, but it's not clear to me what the abstraction-level we have now really gets us. In other words, say we had a BBC micro with a 2Ghz 6502 in it. What productive computing tasks that we do now could it not do? Or let's imagine an Atari ST with a 2Ghz 68000, to get us a little more memory. What could it not do, that we need to do now? I'm struggling to think of anything.