This is true, but if a given foundation (the base principles of a system) was particularly helpful in that context, there would be competitors training in that system. Of course, for competition, the learning curve matters a lot. If you and I are going to compete against each other, and start at a simlar age, etc., then the shorter learning curve has the edge. So a lot of stuff that works over time, simply isn't efficient enough (in learning hours) to be worth getting into - as a system - for competitors.Not true. People don't pick up the system. They pick up techniques from the system and add the techniques, and that's totally different than training a system. For example, a BJJ practitioner may learn Muay Thai low leg kicks and leg checks. But that's not the system that's just 2 techniques from a system.
MMA is full of fighters who have added techniques from other systems but not the entire system. There's a difference between adding a technique and training a system.
That's actually one of the things I love about MMA's development model. For someone who wants the steepest learning curve, MMA has helped drive a lot of places to figure that out.