Insightful philosophers

What if all the most insightful philosophers were solipsists but they didn't bother to write any of it down for others to read

...Which is to say that I've been thinking a lot on the general subject of "what is it that makes an idea valuable?" (which leads to "valuable to whom?") (which leads to "so what is value anyway?" which leads basically nowhere unless you're interested in chipping away at undecidable axiomatic bedrock, which I am not.)