I love Tarn and I think there is some wisdom in the way he develops, and he is clearly brilliant.
But I look at the state of Dwarf Fortress now, and Dwarf Fortress 5 years ago, and I do not see a huge amount of additional features and design space that has been explored.
Even when Tarn decided: "Hmm, maybe making some money for a product I am proud of and work extremely hard on" when he decided to add the Steam version, it has been a long load to make it there.
The game still has FPS death when fortresses get to a certain, actually relatively modest, size. This is a big deal, it means people cannot dig in as deep as they want with their fortresses. Imagine if your Skyrim game choked to death after investing months into a character because of an unspoken, undetectable limitation.
It is an impressive project, but the lesson I always take from his talks is: "Take your time. Build it right. Someday you may have to make a new GUI front-end, and I don't want that to take multiple people multiple years to accomplish."