I'd say the main difficulty is that Dwarf Fortress is a fairly colorful and fun-looking game, a lot of younger and inexperienced video game players are attracted by the fun stories of Boatmurdered and the draw of its simcity-like freedom. DF is a game that can require patience, analytical and critical thinking, spatial awareness, a good memory that can keep track of lots of tiny details, and more. Maybe in 5 years of playing other, perhaps simpler games, they would indeed enjoy DF. But DF is not an instant gratification type of game and the younger and less experienced people are, the more instant gratification is what they're after. So their big mistake is playing DF at all, and then going on to take it lightly and then getting angry or discouraged when their half-assed approach to playing it leaves them staring at Your Fortress Has Crumbled to Its End over and over. Sound fairly close?
Learning all the complex intricacies of how the various buildings, mechanisms, and other tile-pictures interact with each other took me a long time, at least a year of regular play. I still have trouble with pumps and gear assemblies sometimes. I went through stages where I was only good at a particular set of DF skills. I read the wiki a lot. I looked at other peoples' fortresses. I tried again and again, and eventually a lot of the forts failed due to large mistakes. But some I did well with and retired peacefully and overall I learned as I kept playing. I don't recall ever coming to the forums here and complaining that my failures were BECAUSE THE GAME IS TOO HARD. Or that it should be made easier. If anything, information should be easier to come by. I've never attempted to use the help functions in DF because the Wiki is superior for finding what you need to know, but if all the different help screens could be accessed from relevant locations and provided good, illustrated examples of how and why you might use various buildings and their associated orders, it might trick a few of these newer players into focusing on raising their skill instead of asking the game to be toned down. It really isn't a "hard" game, there are no real-time skills involved. It just requires strong awareness of wtf you're doing to be consistent...