I don't know if we have to posit replicators, but we could. They're a convenient metaphor for unlimited mastery over matter, and in particular they're the ultimate automated manufacturing facility.

The thing about replicators is that they're basically magic (or "Godbots" as Steve calls them above), and the discussion's over almost before it starts. When I was talking about robots and automation I guess I was talking about an intermediate stage along the path to the ultimate "magic", something I could relate to the concrete reality of today and sink my teeth into.

With a replicator you don't need dirt or hydroponics to grow a tomato, so that discussion pretty much gets aborted right there.

But at the intermediate level of robots and automation, you need to differentiate between the human labor involved in growing the tomato, and the raw materials. It seems like it'd be entirely feasible to grow tomatoes using a completely automated farm, freeing up humans to do something else. You'd still need the dirt or hydroponics, of course.

This is where we need to talk about the human consequences, and what the society of this utopian future would look like. People can either be freed by automation to do better things, or thrown out into the street to starve. Automation can be a terrible thing for people if it throws them out of work and deprives them of a means of survival. Retraining can help, but it has limits if, economy-wide, the overall pool of available jobs is shrinking because of increased productivity (I think we've been seeing that already for years, but I'll say it in parentheses for fear of triggering another impassioned defense of the status quo from the conservatives). Somehow the utopian world of Star Trek has figured out how to adjust to abundance without destroying people. Unfortunately, Roddenberry and the writers have never let us in on the trick!