One thing I will add to your commentary on science and philosophy is that more recently (the last 30-50 years, especially), several sub-fields of evolutionary biology like evolutionary psychology and sociobiology have begun to fundamentally unlock new ideas about why humans behave in ways they do and why and how we created many aspects of our culture, philosophy, and sense of being (consciousness included). This overlaps significantly with what philosophers have been discussing for millennia, but now we have many more scientific tools to help understand some fundamental questions. These are complementary disciplines for understanding our existence.
I have no use for David Kelley, like I have no professional, personal, moral or ethical use for any Objectivist (if I dropped my wallet around an Objectivist I'd have to think about kicking one home before I bent down to get it, just to be safe), but that Peikoff tried to tell him and his adherents to leave the "Objectivist Movement" because they didn't think philosophy started and stopped with Ayn Rand, because they didn't think that you have to "revere" [Peikoff's word] Rand, because they didn't think it was impossible to consider as potentially valid or edifying other systems (be they Marxism or libertarianism) that had the temerity to not put Ayn Rand on an altar...well, it's telling.
I understand her conclusion as "people study old philosophers, not to learn about their views, but to learn about their thinking techniques". In contrast, I would say that the primary reason for studying old philosophers first-hand is to properly understand philosophy.
(I wouldn't start by studying the old philosophers - I would start by reading modern summaries, especially those that focus on the actual philosophical problems. Study the old philosophers only if you want a full understanding).
You have to understand what philosophy is. It's studying the fundamental nature of reality and our thoughts about it. When you get down to fundamental issues, there are often a very small number of plausible answers, and much of philosophy is extrapolating the consequences of those answers. These issues are timeless and still relevant.
The pervasive modern belief is that philosophy is mostly meaningless word-games that can be dismissed, and science should be the basis of everything. But collecting more observations of reality does not help answer these questions. Furthermore, without knowledge of the implications of certain answers, you easily wind up advocating positions that don't actually hold up. (E.g., many people think neuroscience has disproved the existence of consciousness, when all it has proved is that consciousness is closely related to the brain).
Like Katja, I used to follow Lesswrong-style rationalism, but after studying different philosophies I concluded that Objectivism made the most sense. (Whatever you may have heard about Ayn Rand, I recommend evaluating her views for yourself). Leonard Peikoff gave an excellent and comprehensive course on the history of philosophy from an Objectivist POV: https://campus.aynrand.org/campus-courses/history-of-philoso...