One of the annoying things about "code simplicity" is that it is a subjective trait. Whether a piece of code is simple to understand depends very heavily on what the reader is used to, and that's not something that the writer of the code has much control over.
That has pretty much the same problem. Assembly programs have low "cognitive load" by that definition, but few would say that assembly programs are simpler.
I wouldn't say so. When you're on assembly programs, you hold things like "register values" in your head as well as other low-level things. It's not only about abstractions and language features.
And unlike registers and memory addresses, you don't really have to juggle regular variables in your head unless the program has a lot of unnecessary mutability, or really bad variable names.
x64 has 16 general-purpose registers. "Much lower" starts somewhere around a half. I say, touching 32 variables in a given scope is not "half complicated", it's sabotage.
Not really, assembly has much more cognitive load. Try reading more than a trivial chunk of assembly and you'll see you can get overwhelmed pretty quickly by the amount of information you have to remember. You have to memorize code paths, which register or address has what, offsets of structures, juggle registers.
