As a late-comer to Glorantha(1), I have to say that the 2 most confusing or annoying parts of the product line are:
Recommendations of out-of-print products. You can thankfully get the PDFs (and I'm super thankful for that, I hope more PDFs show up eventually) but I find that it's not as fun to flip through, and not as practical for "reference" type books. I understand that it's still better than "nope, there's nothing about Sartarite culture available right now" but I think it might be worth it to always add a disclaimer that only the PDF is available. And I don't mean to criticize specifically people who posted about Sartar books here, I appreciate the information and help, I'm just sharing how, at first, I would often feel a bit of disappointment tracing back some book reference to a PDF-only page (or worse).
The tribal knowledge surrounding the convoluted publication history of both Runequest and Glorantha material. Sometimes there's material that has been re-published with minor edits, sometimes there's new material that invalidates older material, etc. I would absolutely LOVE to see a list of all the books ever made by the usual suspects (Chaosium, Issaries, Moon Design, Mongoose, etc) split in a handful of categories that help figure out what you're getting in terms of Gloranthan canon-ness ("currently canon", "compatible with current canon", "mostly compatible, see notes", "mostly incompatible"), dates covered (second age, third age, which dates, etc.). I understand that it's possibly a massive amount of work, though. The Glorantha Wiki actually helps a bit there sometimes.
(1) I've been gaming for a couple decades and along the way collected a couple HeroQuest books to flip through casually, but I started looking at RQ and Glorantha "seriously" only recently thanks to the Chaosium revival.