Complexity as an option is never un-needed. I suggest it BECAUSE we need it. Table Tops are based on two base mechanics, Mathematics, and Customisabilty to the player's needs.
Not every game is Core D20. When playing a system with user variables, calculations can get very convoluted.
One of the benefits of ROLL20, and the reason I pay for it, is the automation of some of the 'Game Slowing' elements of D20. (Such as spending an hour arguing the proper way to calculate the math).
I want it all templated for my players, so they don't need to think about it. And that requires that I be able to have stats display and calculate according to their needs. Which, right now, it doesn't.
But I can respect your desire for simplicity. I believe that there will come a time when ROLL20 DMs are required to load 'Modules' into their campaign, such as 'Advanced Math', 'Advanced Profile Controls' etc.
Assuming that the Developers are headed toward a system which can handle the creation and execution of any Table Top math system, the advanced features will get very complicated.