Design thinking is a mindset. Everyone is capable of deferring judgement and building on others' ideas, but most people haven't developed the mental discipline to suppress their instinct to immediately point out faults in half-baked ideas. As a result, even after teams run training sessions on design thinking, they likely still need outside gurus to help them because it isn't a skill that can be internalized quickly. It's something that needs to be practiced.
Many people downplay the value of design thinking because it sounds easy. Like most things that look easy, it's hard until it's second nature. In concept, juggling a soccer ball is easy. But, once you try, you realize that it takes lots of practice for it to look so effortless. If you believe in the value of design thinking, take time to practice your mental discipline.