Well, it may also be a reflection of escapism playing an increasing role in Japanese life. When surveys are showing about 70 percent of non-married, Japanese, 20-something males don't have a girlfriend, and about 25 percent of 30-to-35-year-old males being outright virgins, that audience will look for fantasies to escape in, and anime is uniquely good for providing that. If you're 40 and you've never had a girlfriend, yeah, moe is going to hold a place in your heart.
Well, the flipside is with that old-fashioned style come a few different issues in marketability because of those internal demographic issues.
-Real characters with depth can't act as templates for which otaku can simply affix all their desires on to. Shoot, when the otakucentric and relatively cookie-cutter Kannagi implied one of it's characters might not be a virgin, there was an uproar amongst otaku. Someone as realistic and complex as Asuka or Ninamori might be just too out there for these folks. This may be why you see Rei-clones so often - they are templates to affix whatever you want to. (Plus, no one gets that is exactly what Rei rebels against in End of Eva. She chooses her own destiny, not the affixed to her by Gendo. It was commentary on the part of Anno.)
-Complex stories often demand of the viewer at a minimum critical thinking if not outright introspection - something a lot of these guys may not be hot to do if they are grinding away at a low-paying job with no girlfriend, let alone if they're a NEET or hikikomori. There, moe is the stress relief at the end of the day: "My job has no future, I've got a degree from a third-rate college, I can't get a girl because I'm barely above the poverty line and I still live with my parents, but you're my friend fictional 12-year-old! I'm gonna buy body-pillows and figurines of you for about 6 months to a year, then get bored and find a new fictional character to drown my pain in! Maybe she'll be a vampire!" Something like Eva or Lain or FLCL or Haibane or what have you means they'd have to rethink what they're doing. Moe kills the pain.
-Retro situations are evocative of their youth - when they still thought maybe they were going to get a good job in upper management and marry some cute girl. Nostalgia -> Introspection -> Sadness.
Given the previously mentioned demographic issues, I'm skeptical, though if the industry cannibalizes itself by destroying the export market, it might, after a bust, re-normalize. Besides, self-produced visual novels, manga and soon anime should hopefully soak up a lot of that demographic driven demand for that content. Of course, just as likely is self-produced works become a haven for the real artists while big studios mostly crank out shows for lonely dudes. I can't blame them for the easy sale, but they'll always be chasing the next thing with that kind of minRABet.