The changes have little effect on JWs because they are rarely aware of them. When I was a JW, I felt confident that I knew the organization's history better than any outsider. How could I not? I was a JW! I had the books, and those books had the history, and I had lived that life for decades.
Then I get out, start reading, and am surprised to find that I knew almost nothing about the organization's history. What little I did know what severely skewed by the WTS to present the version they wanted me to know. And then I realized that JWs know less about their own religious organization than most people, because even the stuff we do know is false or so skewed that it may as well be false.
And frankly, the concept of "new light" is a convenient cover for the fact that religious beliefs have to change as humanity learns more about ourselves and the world around us. The illumination isn't coming from god; it's coming from people. Even today, after more than two thousand years, we still can't agree on what the Bible says or means in a lot of places. How 'bright' can it be?