I mean, I am also new to RQ. I'm 31, so I am too young to have been a RQ3 grognard (to bring it back to the thread topic a bit!). I was interested in older forms of D&D (I used to run an open table D&D session using the original 1974 rules--by the way, the Jack O'Bear is based on the original pumpkin-headed bugbear illustration from Supplement I: Greyhawk!), and I ran across a discussion about RuneQuest on one of the old school D&D forums. Classic had come out, so I bought that and got very into it but held off on running it because I knew the new edition was coming out. I also checked out Mythras (their Monster Island module is great), but it's a little too crunchy for me to run. Anyway, I got into Glorantha but held off on running a campaign because I knew the new edition was coming. I considered running HQ, but after playing HQ for the first time I concluded it was probably a little too free-form for my player group (great game though if you have a particularly imaginative group). My main exposure to RuneQuest is only what's available through Chaosium right now. So that means not much RQ3 content. I wouldn't be surprised if people who knew about RuneQuest found out just by browsing the Chaosium website. But that means you'll have people like me who know RQ2 and RQG but not RQ3. When people talk about the superiority of such and such RQ3 rule, I just have to take your word for it!
You're saying that you're worried people won't even be aware of RQG. I mean, that's also a question of marketing and promotion. It seems to me Chaosium has been trying to roll it out in a big way. I know the Quickstart's timing was a bit off, but that they decided to do a livestream to launch it, and chose an already established streamer group to do it, is an indication that they are serious about promoting it. I am not the biggest Actual Play viewer, but it's a huge part of the tabletop scene now, driving D&D growth, and that they knew to launch it that way makes me confident they'll promote it well. I watched the RQG stream live and answered questions in chat about the game to the best of my abilities and knowledge (which is so very meager compared to some of the minds on the Glorantha subforum here!). But also the product itself has to have some hooks to appeal to new gamers. That's not only a matter of the written content, but also the way it's presented. That edge in presentation can immediately grab people. RQG not only looks better than pretty much anything else out there, it also looks different. It's not a generic fantasy world, so people who want to branch out from the blandness of the Forgotten Realms may find it intriguing.
Of course, the rollout is also subject to financial pressures, not having a huge staff, and at this point being known only for Cthulhu among the D&D set. But given these constraints I think Chaosium is doing a great job. I'd love to see them convince a streamer to launch a RQG campaign as that could bring in a lot of people.
On the financial side too it's worth noting that more books are sold than actually played. Having it double as an art book is pretty nice for those isolated people who don't have the chance to actually play it.
EDIT: Apologies for the wall of text! feel free to skim or skip