Pretty much this, to be honest. Dwarf Fortress is not, and probably can not be, a perfect simulation of reality. The game treats "the labor theory of value" as a law of physics, for example, and so the only economic system that *can* function for any length of time without direct intervention is communism.
I disagree. While something like modern-day market capitalism would probably not be possible, simulating "scientific socialism" and all that entails wouldn't be possible either. Any tried human economic system, from "hydraulic despotism" to "religious communism" or whatever you can think of is too complex if you attempt to simulate it perfectly. Communism, as far as I understand it, also needs "direct intervention" to be implemented, unless we are talking about the game being stuck with an extremely simplistic economic framework (basically the one we have right now). I hope that's not the case.
But even if it does, what we currently have in dwarf fortress is a very strage system that's incredibly authoritarian yet arbitrarily (and even bizarrily) communal in some aspects, with some basic goods like food and clothes apparently shared but not distributed, where the greedly take whatever they want. You can give your dwarves whatever you want in terms of rooms and furniture, and all they can do in turn is throw tantrums if they feel like they haven't been given enough. Only the nobility demands better accomodations more aggressively, and there are no guarantees for anyone, etc. I guess that if you squint and tilt your head 90 degrees it could maybe remind some people of communism, but not really.
We have no real idea of what Toady is going to do with the economy. He talked of fairs and markets, so there's that. That doesn't exclude the possibility of us ending up with a quasi-communist system of society as our only real option but it doesn't mean that these are the limitations of what he can do. It will all deppend on how the Fortress Starting Scenarios release go (where they will touch on expanding the framework of law, custom, rights, property and status), and how well that is implemented.
Personally, I feel like rich vs poor, people owning shops, etc, will be implemented one way or another just because those are the kind of features that bring up interesting narratives to the game. What was the last RPG, western or otherwise, where you didn't see that as a thing? It's very common and useful. Also, it's just interesting. That is why bringing the economy back but functional this time is so important to a lot of people. Maybe it will never be fully implemented because it wouldn't work with the mechanics of the game, but I think it's worth a try.
To say dwarven society is ideally this or that system because Toady has yet to code the elements of an economic simulation is as fundamentally flawed as saying humans are not intended to fly because God did not give us wings.
That's probably the case. Hopefully, coding these elements is not only Toady's intention, but also feasible, because admitedly it does sound really complicated to implement things like realistic fluctuating values of goods, etc.