If you wanna get more materialist, the “both sides” concept as most people know it is flawed from the beginning. A communist could choose to see two sides like proletariat and bourgeoisie (which itself is true in a way, but still oversimplified) or like the thesis and antithesis of any given contradiction. But that’s not what most people mean. The common left versus right paradigm is just idealist bunk and ignores a vast amount of intricate contradictions, chiefly class struggle. You were correct to choose Marxism instead.