Hi!
Idiom: I am not sure what you mean with easier to pick up. While z-levels are kind of a complication, the simplified surface farming makes more than up for that. I remember that in 2D it took quite some try and error to get the balance to get past the first winter without a major tantrum chain and the need for irrigation put more than one fortress to a watery grave. In 3D, food is obtained extremely easily - even hunting works properly!!
As for the general discussion here, I am not sure whether I can agree with the original supposition. It is true that some built-in features have died (like specialized ruins for adventurer mode), but they have gotten their replacement (albeit sometimes in a weakened form).
If you want diversity/interesting things in your fortress mode game, make sure that you have at least two biomes in your embark site, preferably more. And don't use the site locator and have all features hidden (or only finder revealed).
Sure, you are running the risk of not having certain fun features, but you will only know after you have thoroughly explored the map.
Also, I don't think that the current game is terribly standardized/boring, even in its standard conditions.
Initially, you have to deal with the surface structure, either levelling hills or integrating them into your defenses. If there is a surface brook or river (shudder), you may also wish to consider that.
Then you have to explore the deeper layers of the map without really knowing what to expect. You may find good stuff or bad stuff and you have to figure out how to make the most out of it.
And finally, if you don't exploit the over-powered cage traps, the interaction with the goblins and megabeasts is bound to be improved as they tend to have learned from the past.
In adventurer mode, while special sites and the easy wars are not present, there can be more to discover in the history of the world. And there are always little surprises (like a mayor in a town of a friendly civ consistantly killing your adventurers on sight).
If anything, you may say that fortress mode has become easier and together with exploits like the cage traps, it can be too easy. But if you don't use such exploits and don't turn your adventurer into a master thrower of vomit, I think the game has both challenge and diversity enough in its current form.
At least these are my thoughts, and I don't really miss the 2D times, sorry.
Deathworks