Kind learning environments are areas where you can find repetitive patterns and build up experience in detecting such patterns. The feedback loop is short in these environments, allowing you to correct the course faster.
Chess, Tennis, Golf, and many other sports are kind environments. They operate by a fixed set of rules where experience and deliberate practice can make you an expert.
On the opposite spectrum, we have wicked environments. There is no pattern in such environments, some information is hidden, and relying on experience can derail you toward the wrong solution. The feedback loop is slow, often taking many years to see the result of your actions.
Real-world problems tend to be wicked. For example, dealing with climate change, poverty, hunger, large-scale conflicts, and wars.