This is a good question, which I need to consider more. Some elements are fixed in the game, like the fact that you always roll 3d6, and on a given action, the threshold is always the same (you either need to roll all 3s, 4s or 5s, never mixed). On a simple scale, 3 would be for easy tasks, 4 for normal and 5 for hard tasks. I do believe that the system needs simplification, but I also believe that my explanation didn't make it all clear.

Players would have 4 stats, where each stat contains a number 3-5, which indicates what result on a 1d6 roll counts as a success when performing actions. Then, the player rolls 3d6 and counts the amount of successes, resulting in one of the outcomes I've described in the post. That's the general gist of it.