Software industry developed strong preference towards simplification. We have important principles like KISS and YAGNI in our toolbox. We keep hearing "stop over-engineering" from leading experts in the industry. But we must not forget the distinction between essential and accidental complexity. A number of biases, completely natural for human brain, are effectively lead us to over-simplify problems we are working. Many of the UI and UX issues we around us are caused by intolerable level of ignorance, demonstrated by people who created those products and solutions. The only efficient way to fight this tendency is to realise and embrace the complexity. This talk will focus on demonstrating the issue and providing advise on engaging our cognitive abilities in order to solve complex problems.