Depends a lot on what you are building. If you're talking about a von Neumann machine with symmetric registers -- basically a PDP-11 derivative aka "C machine" -- then you're right: you "simply" have the hard part of, you know, designing a chip, which is an art, and at any appreciable clock frequency, de facto mixes digital and analog design.

But as soon as your stray off that path you're on your own (and you still have the chip design problems as well). The Mill guys have been at it 14+ years (admittedly none full time AFAICT).