Their creation has a bad UI. The barrier is a part of the work. You could take the swearing out of The Godfather in order to make it more accessible, but what people would be accessing would not really be The Godfather anymore.
If you're talking about the interface design, keyboard commands etc, ignore this comment.
If you're talking about the ASCII art I would say it absolutely is deliberate. DF is actually a sequel (Slaves to Armok, God of Blood, Chapter 2: Dwarf Fortress) and the first game was 3D. They chose to make DF a roguelike ASCII art game because if they had tried anything else, it wouldn't be half as deep as it is now. The ASCII art enables the depth that the game has developed.
As I said, if you are primarily arguing that they should keep the ASCII art and revamp the interface, you can safely ignore this comment.