I kind of think the different styles an systems are like dog breeds. I've read, that if left alone, all dogs would look like a pit, a wolf, or a dingo. Humans started selectively breeding dogs with particular traits and created "breeds". I look at fighting the same way. "Mixed martial arts"? Martial arts have been mixed for as long as cultures have. I think humans kinda broke fighting into categories then focused on that particular element of fighting. Also human tried to replicate what certain (skilled) people/fighters did, copied them, taught others how to imitate them and that morphed into a "ryu".
Are styles dying out? Were they ever a real thing to begin with?