I have to agree with both you and @Bill Mattocks. Fundamentally, the mechanics of most kicks have not changed greatly however, the variety of kicks (even within the same kick) has. And fight strategy has changed exponentially.The thing is. MMA is a very different beast than what once worked in the UFC.
It is not a product of fashion so much as a product of technology. In that we can access elite level training from anywhere in the world.
And there are levels to fighting.
Superior communication was the super secret.