Hopefully we won't go back to the Win95/98 era of everything running as single user!

Having services run isolated as their own users is not merely a good security mechanics, it provides for a clear and simple mental model of what is what. A clear permissions barrier that's enforced pretty strictly by the OS.

Moreover we see separate user accounts more and more; even on small devices like phones it makes sense to have, for example, separate "private" and "business" accounts.

>does that mean processes have failed?

Nah, that's too general of a take. There are two more specific failures. First up, people fail to realize the present-day crop of containers are re-inventing processes. "Those who do not learn history, etc, etc."

Secondly, there's a significant failure of certain key features (like IP stack, FS handlers, etc. - in general, NAMESPACES) having been provided almost exclusively in kernel, and thusly requiring either superuser access or complex work-arounds (like FUSE) to manage. Plan 9 did it the right way; on P9, processes == containers.