How is that any different than a daemon that has a parser error in its message handler, except that the daemon could be misconfigured to listen on a network socket?

The original unix process abstraction was extremely simple; the entire spec is a few pages.

The problem is that Linux keeps adding more and more levels of Rube Goldberg machine to its security model, so now literally no one understands how a default minimal install of, say, Ubuntu works.

Adding a magic daemon that runs stuff as root to this pile of complexity probably won’t help. Ripping out almost all the cruft that’s accumulated over the years, and adding back something sane (maybe BSD jails) would work a lot better.