I'm a traditional Karate man myself, so I will do my best to keep my answer as unbiased as possible.
Basics are the foundation of almost any (if not all martial arts.) And as my one instructor once told me you have to practice a technique not a hundred but thousands of times before your body 'knows' the technique to the point where it can perform it automatically to place the technique where it needs to go etc.
Kata is a practice of basics, repeating them over and over again, starting with basic techniques and then as you get into more advanced katas, obviously more advanced techniques.
Now, practicing the kata is absolutely no good if you don't use the moves your learning need to be polished either with the heavy bag and with sparring.
So, katas are great, and they work as practice tools but for more 'practical' training you need to get out there and spar!