Avoiding Theory will teach you nothing
Since i used to be one of those amateurs who play less common openings to avoid studying i feel entitled to state that such mindset is totally wrong. Please don't avoid playing the open Sicilian, the Ruy Lopez, or whatever opening is scaring you. Please refrain from playing openings like the Bird, or zero theory systems against the Sicilian, or the Four Knights to avoid the Lopez, or systems with Na6-Nc7 to avoid the main lines in the Caro-Kann, playing g6 against anything just because GMs can do it, etc. You are missing a great deal of chess. You won't get better that way!
Instead play those openings and learn how to play them by playing them! Study GM games in those opening and you'll soon find yourself playing better games.
Opening books that really explain the ideas behind the opening are very rare and usually they focus on that particular sub-system that the GM wants to teach you (usually it's a system chosen so that you don't have to study too much). Amazingly you can find excellent insights on opening ideas and plans in books whose subject is not the opening! Games collections mostly or all those books of the "Amateur vs Master" type, even books aimed at kids!
Throw away all your opening books (90% of them are only marketing hype) and start PLAYING...NOW!!! Studying opening books is the wrong way of studying the opening. The opening theory is not in the books it is in GM games! Study the games! Find annotated games in those openings and you'll magically understand why your favourite GM is playing those misterious moves in the middlegame!