IIRC, mouse support in DF is going to go way up in the next update. That alone will make things much less painful.
There are several issues with DF's UI. There's so much information that needs to be displayed sometimes, and there's no text scaling. So you need multiple sub-menus, which all end up looking the same, and create a lot of eyestrain as you constantly scan menu items hour after hour.
This is most problematic with creatures and dwarves. Those lists just become overwhelming to scan through repeatedly once your fortress is big.
The in-game real estate also isn't optimized to provide information. The menu cheatsheet already take up a big honkin' chunk of it. And again, no text scaling is a big problem. If you could cut that menu in half, and replace the gap with a unit card that displayed VERY basic information, you could pretty much set the cursor default to "Look around." And that would be one less button the players has to hit to get information.
Lastly, most information not being shown on the game screen is presented as text, and that's again a limitation of the ASCII. Having things like easy to read icons to represent rooms, animals, jobs, items, ect...in lists would make all the visual scanning you need to do a lot less tedious.
For DF to get to even like, a Warcraft 1 level of display would take a good year or two, especially since the whole game has to make the jump from text/ASCII to real art assets. I'm sure there's no shortage of people who could help with that, but it will still take time to apply that to whole game and for Toady to settle on what visual style he prefers the most.
Not decades, but yeah, years. And it will be an iterative process too, like everything else, done in bits and pieces. As much as he'd like to satisfy DF fans visually, I'm sure he doesn't want to leave gameplay out in the cold for a solid year or two working on it.