Why is this repertoire called simple? For the simple reason that the variations are straightforward, easy to remember and require little or no maintenance. International Master Christof Sielecki has created a reliable set of lines for chess players of almost all levels. The major objective is to dominate Black in the opening, by simple means. You don't need to sacrifice anything or memorize long tactical lines. Unless Black plays something stupid, when tactics are the simplest punishment.
Sielecki developed this repertoire working with students who were looking for something that was easy to understand and to learn. Most of the lines he selected are occasionally played by grandmasters, but on the whole they lie outside the mainstream of opening theory. That means that there is hardly any need to monitor theoretical developments.
Sielecki always clearly explains the plans and counterplans and keeps you focussed on what the position requires. Ambitious...