Well, I can agree with the OP with regards to complexity and detail, and in fact would actually take it a little further: When you get right down to it, this game's economy isn't complex at all. It doesn't even match the complexity of games like Emperor or Pharoah (Sierra Citybuilder games), which are both older and less ambitious games.
Seriously, this is all you really need:
http://df.magmawiki.com/index.php/Industry And the game basically breaks down into four raw materials: stone, metal, wood, and food. And most of those only have two tiers at most of production, generally speaking, you can just turn stone directly into virtually anything you need, and all you require is the proper workshop for making that one specific kind of good. Which workshop do you really need? Who cares! Build them all! They all only require one stone to build, which is so common you literally can't get rid of it fast enough, and can be deconstructed almost instantly if you make a mistake. Just build workshops until you find one that builds what you want.
Dwarves have needs, yes, but they're so simple and basic that it's pretty hilarious - food, drink (which is just food that has been to a still), a bed, maybe a dining hall that will keep them ultra-happy, and a relatively secure fort. Only that last one is remotely difficult to satisfy, and a simple wooden door is generally enough to keep many threats out, and backing that door up with enough cage traps and stonefall traps solves the rest.
So, what else is in the game?
Geology is nice, but you don't really have to care, especially now that with enough layers, you're guaranteed to get everything you want besides sand, anyway.
There was this thread on obsidian that expanded into vulcanism in general: (
http://www.bay12forums.com/smf/index.php?topic=61946.0)... we have exemplars of mafic, intermediate, and felsic rocks for both igneous extrusive and igneous intrusive stones... but they don't really matter, as they aren't in any way meaningfully distinguished from one another, with the exception of Gabbro (mafic intrusive) occasionally having Kimberlite (which is actually supermafic intrusive stone that makes up much of the real world's mantle, but which was only created roughly around the time the earth was entirely molten), which very rarely has diamonds. It would be a complex game feature to have actual magma flows that track the magnesium and iron (mafic) quantities of the magma, losing those minerals to quartz deposits as the magma matures into felsic magma, potentially generating pressure and turning into pyroclastic felsic volcanos or even just having runny mafic volcanos... but all magma is the same, and you find different kinds of igneous intrusive stacked on top of one another haphazardly because the game can't tell the difference between one or the other.
Individual training and injuries and hospitals are unique highlights, but generally, the military works as a simple "stack mash"-type combat for those who want to see this game in its most simple terms possible - like most 4X games, you can simply build units with bigger numbers and if that isn't possible, just make a "bigger stack" of units, and then just open the gates, and throw them at the enemy - no strategy possible, much less required. The biggest stack of numbers wins. Quality in DF far outstrips quantity, and as such, lone champions can essentially single-handedly sweep whole battlefields of inferior troops with inferior weapons and armor.
Yes, the "learning cliff" of this game is largely in the presentation - you have to go somewhere else to read what it is you need to do in order to survive. Yes, a "tutorial mode" with pop-ups or whatever would help this...
However, once you have "survival" accomplished, the problem is that there isn't much beyond that at this point. It's just details that are meaningless (who remembers the facial features of any dwarf beyond their starting seven?) Nothing but HFS or maybe a really, really lucky roll on the procedurally generated creatures table making things like giant crabs that breathe incindiary sleep gas, or just plain FPS decay will seriously threaten your fort.
What the game needs are more serious complexities to running an established fort to keep the game interesting beyond just making megaprojects and occasionally pulling the "Boatmurder" lever to wipe out yet another goblin seige.