There are things in you list that need communication with someone (web and apps - I'd wager they are underspecified). I think you do not need communication working on retro assembly.
I am working on IDE supporting two dirty old languages, VHDL and Verilog. I need three things opened: Visual Studio, PDF of standard under question and orthodox file manager [1] in the tests directory. Having internalized a great deal of VHDL, I do not need it's PDF opened too often. So, there are two things for me to work with: run tests in VS, occasionally look at problematic source code with OFM.
I also need a great deal of silence around me, otherwise I cannot concentrate deep enough to make good decisions and implementation of dirty old languages badly needs extremely good decisions.
Capitalism specialized labor where it was cheaper - mass production. This has since been automated. Subject matter experts have always been valuable, but such diverse experience is hard to come by.
Moreso it's about having to wait for the technology. Waiting for the page to load. Waiting for the program to load. Waiting for the IDE to load. Waiting for 1 million FOR loops. And having something else to work on while you wait. Or just something to read, or watch. Maybe even for a personal project in an unrelated field, or just to be a more interesting person.
> A person who dominates a set of skills in both breadth and depth. In other words, this person possesses a lot of skills but excels in 1 exclusively.
Better to excel in all skills in the field than one exclusively. Even better to excel in a multitude of skills across numerous fields. But such diverse experience is, of course, hard to come by.