In our modern age of information technology and easy travel, we can access instruction in many different methods much much more easily than people could in 18th century Okinawa. We have access to much more information that we can learn from, we have the ability and the tools to research more thoroughly than before. I think people today have the definite potential to be more knowledgeable and more skilled than people of the past, with some limitations.
I personally do not hold myself out to be one of those people.
That being said, nothing that we practice now, based on older methods, was handed down from the gods in a state of perfection. It was all devised by people, and they had the same shortcomings and failures that people today have. They too made mistakes, or did things one way that could have been done better another way. None of it is sacred. It can all be changed, either minorly or majorly.
I personally do not believe that anything today is being done exactly as it was first created, if it has been passed along for more than one generation. Even then, I doubt it. People are different, they will understand things differently from each other, even if only a little bit differently. Already, it is different.
People do things to the best of their understanding. This can cause it to be different from their teachers, even if they BELIEVE it to be the same. The next generation of teachers teach to the best of their ability. That ability is not identical to their own teachers. Again, this leads to differences.
I think it is a myth to believe that any system or kata or whatever has remained completely true to that created by the founder, regardless of intentions. But this does not mean that it is not still the same system.
As long as the intention is to maintain the same high level of integrity and quality, then it is still the same system, even though it changes, and even if some changes are deliberate.