Code katas are simple exercises that are meant to be repeated. They are great for learning a new language or tool. The goal is to learn something, not to complete them. In fact, if you don't finish a kata that is perfectly normal as long as you take something away. The beauty of code katas is they are small enough to be repeated and possibly completed within small time slots.
Beginner or expert there will be something you can learn or take away. Beginners should take away language skills, tooling tricks and more. This is furthered when pair programming.
Experts should be inclined to try new solutions rather than rinse repeat. Instead of solving the problem in the manner you do 9-5, try something completely new. Solving a kata ten times the same way is a waste. Instead solve it once, ten different ways. In short, experiment in code katas, not your production code.
Sadly a small minority seem such simple exercises as below them. No one is above doing a kata. Constant improvement or training is essential regardless of level. Katas alone are not enough to support personal development. Experience, reading and practical development are all still required. However when code katas are combined they are an excellent aid.