Richard Rudd was a student of Ra's, taught HD for years and once said "We don't need Human Design" (I def disagree) but I also feel that Ra is not the sole bearer of the HD knowledge. It has existed in different forms before he received his download (mainly the I Ching and Kabbalah) His download brought it together in a new way but still channeled through his lens. I have been studying HD for over 2 years and I still feel like I don't know 80% of it. It is something that is learned differently be each individual based on their design. The issue we face now is that HD while INCREDIBLY powerful is SO complex that many people give up on it before they even get to the valuable part that can help them. I think Gene Keys can help many more people. HD + Gene Keys together is in my opinion really really transformative, but you need to know your keys, your lines and get the Gene Key book. I can send anyone who wants one a PDF. This is also a good video to understand why we might need both:
https://www.youtube.com/watch?v=031JSauBj-4