I don't want to try and answer whether it's really neglected or not. My personal experience is that I haven't seen an approach as reasonable, methodical and clear as this one (so fa in my reading).
In a sense I'm saying the opposite of what you think I am. I'm saying that the whole topic under discussion has been broadly under discussion since the beginning of recorded civilisation. So saying "strangely, the topic as a whole is never addressed" seems a tad like a new minted programmer saying "strangely no-one has addressed the entire topic of OO programming".
This isn't to say that philosophy has already asked and answered every possible question, just that the most obvious versions of these (obvious for the kinds of people who would bother doing this in the first place, i.e. relatively intelligent people) probably have good discussions going on and that the philosophy of those questions is more about joining that discussion and adding your perspective (if it's new) than about formulating original paradigms and meta-narratives for solving them, because that's been done already for a lot of questions.
The problem is that you often can't really find this through Google, unless you know the name we've given it (or happen to phrase your question in almost the same way someone else did on StackExchange). That's why it is so valuable to have a good human search engine to talke to (say, a professor who knows their field really well).
The author is pretty well known, technically, and has been applying Buddhist-style inquiry patterns to a western vernacular for a long time. I don't think the knee-jerk cynicism is warranted. You may disagree with his conclusions, but he isn't a superficial guy.
And the fact that you think a search for meaning outside traditional religious models is 'mysteriously neglected' is baffling. Nothing in your comment seems to correspond to David's work, as far as I can tell.