Morihei Ueshiba is considered a genius by many. Some technique taxonomists have estimated he had some 10,000 techniques. The tradition he came from was Daito Ryu AikiJujitsu. Daito Ryu was primarily spread by Sokaku Takeda. Similarly I have read some branches of Daito Ryu have so many kata they claim also to have 10,000 techniques.
While in their own rights both Morihei and Sokaku were great budo men, Mr Tomiki came along to study in their shadow. He was a physical educator that took a long look at what Ueshiba was doing. After many years of tinkering he formulated a system that contained the core ideas and principles of the 10,000 motions Ueshiba demonstrated.
The genius of Tomiki lies in the fact he made a physical equation to simply the understanding of the movement of Aikido. Eventually he boiled it down to 17 ideas of motion, what we call the junana hon kata. The simplified Aiki system was meant to teach people the ideas more quickly.
I am willing to bet these 17 ideas are more than most artists will ever really master in a lifetime. I know I have not even come close.
It appears that Tomiki Sensei and his core of close students and comrades became prolific kata writers. The students of all these people continued to write more and more katas, and now a mere 30 years after his death the amount of kata under the umbrella of Tomiki Ryu is staggering. The genius of the 17 techniques has returned to 10,000. Some teachers even claim you must learn them all to understand the system.
I myself see the beauty in aikido is in simplicity. To study simplicity is a study of what I believe the intention and design of the 17. While the advanced katas are fun and useful, it is my assertation that endlessly grinding through kata is not the only, or even most efficient way to absorb the lessons of the Tomiki Ryu system of aikido.
As a related side note, if you look at statistics of sumo and judo players you will find they tend to score the same 4 techniques over and over. Good advice from the pros...simplify.