I shall speak from the point of view of a player who enjoys playing Dwarf Fortress, and its different Mods (and Mods for different games, in general).
I suppose one of the major problems with Mods for Dwarf Fortress, especially mini-mods, is that there is no way of quickly managing them, browsing through them, etc. When I started playing Dwarf Fortress all I did was add a graphics pack, then when I learned to change playable races and edit the Raws I begin playing the different races in the game, with a bit of editing of course. It was nothing advanced, merely calling for a bit of editing and questions on the forums.
The first "mod pack" I discovered was the Newbie Pack (I believe it was called) that had all the different utilities and mods installed, and it all worked perfectly. I am relatively new to Masterwork DF and I really liked it for a few things:
1) Simplicity, the GUI really helps in managing your pre-game where otherwise you would have to dig into the Raws and find the correct parameters. It has a long selection of graphical mods and even fonts. It has custom races, which was the one thing that caught my attention primarily, but most importantly I can quickly and easilly switch between them.
2) Everything in one package. Like in the case of the Newb Pack everything you could possibly need is there. You even have handy options to turn off the things you do not want or need. If you are not skilled in "operating" DF then you could have a massive headache adding the different races individually, making sure they work properly, etc. Masterwork does that for you.
3) It's great for beginners. When I speak with my friends and other games and they hear my stories about DF and want to try it on their own I direct them to mod packs such as Masterwork or Newb Pack, because they offer a LOT of help to somebody who is just starting out. When I begun playing Dwarf Fortress Vanilla I had no idea what I was doing, and it took a LOT of time to break through the learning curve to understand what I was doing. While the races in Masterwork are different to the Vanilla Dwarves they are, in some ways, much easier to play.
All of that said, an issue with Dwarf Fortress Mods, in general, is that unless a person has heard of a specific mod, or knows where to look for them, he won't be able to quickly select the content he is after. I am sure there are countless different Mods that people should try, but how can somebody learn of them if they are not clearly listed somewhere.
The simplest solution is something akin to MODDB, where all the different mods could be listed, and sorted into different categories (graphical, race, utility, etc.). That was a person could quickly search through them and find the ones he wants. However, the problem of installation may persist, even if it's something as simple as copy-pasting a file. If Dwarf Fortress had a way of quickly managing Mods, similar to what X3 had eventually, then people would be able to do just that.
Yet, DF is still a game in development, and Masterwork, and I imagine many other mods, may be "outdated", until the newest version becomes stable and the mods can be adapted to it. As such creating a central platform might not yet be possible, to offer equal "Modding" rights, since who knows when DF will be in a "perfect" state?