I don't think DF needs mass appeal. It doesn't need to attract a large fan base. Modern games have dumbed down significantly in an effort to broaden their appeal.
Aside from graphics, which I'm really not too fussed about, a couple things hurt my ability to play this game, and I've been playing it for years.
UI consistency. Take lists, for example. Some lists are scrolled with the up and down keys, and you can move from the outer list (left side) to the inner list (right side) using left and right.
Other identically laid out lists require +/- to scroll the left list, and up/down to scroll the right (inner) list, and left/right do nothing. Some times you increase quantities with +/-, sometimes with left/right.
Some times you press 'v' to view an item, sometimes you press Enter. Often you need to press 'v',Enter,'v' to view items in containers.
The key to build blocks in a Carpenters Workshop is 'o', but it's 'b' to build blocks in a Mason's Workshop (or the other way round!).
The 2nd thing is FPS. The game desperately needs to be able to recognise low-FPS situations and take corrective action (somehow). Whether that is enforcing an item cap or improving pathfinding or some other means.
The final thing is in the category of "annoyances". This includes undead hands that are able to swing punches (ie phantom bodies), stockpiles that generate cancel spam when inside burrows, and metal barrels being 100% inferior to metal pots in almost all situations, yet costing 3x more materials and being far heavier.