It was absolutely a plot device; they’ve said as much. The rest is just the in-story rationalizations to give viewers something - however difficult to believe - to accept so the story can go forward.

Star Trek is full of these. TNG was chock fucking full of Mordor Eagle plot devices. Quark is Harry Mudd, with a bumpy head. The Federation exists within a universe of civilizations which haven’t yet reached post-scarcity and, frankly, I think even in a post scarcity utopia we’ll still have money and be trading. Consider, we’ll probably still have the very first profession, and you’ll likely have other services. You’ll still have a lot of people like McCoy, who reject the technological solution and want “the real thing” and not a holodeck.