Just my 2 cents based on my own experience. I am a thirty-something, and most of my friends are the same age more or less. I think there are a few catagories these people fall into that helps explain what you have noticed.
1) Believe its "the truth"....but.....meh. - These are the ones that were raised in it and came back later, that had kids and felt like they shoud raise them in the hall. The ones that go to meetings, don't study, show up for social events, can't explain a damn thing, and would get defensive if you attacked their faith. They probably wouldn't shun you in private if you were disfellowshipped. They won't discuss "spiritual things" outside of the hall. They don't comment.
2) Status workers - This includes the serve where the need is great, but really just live near a beach in Peru, class. They do stuff, like join the RBC, go to another country, because its fun and gives a sense of community. Quick to tell others about their exploits, they usually do so because its impressive to the group back home. these people will talk about events, more than actual biblical matters. This can also include (and usually does), young elders, workers in construction that volunteer, people that go to international conventions, people that attend whatever special school is the hot topic, etc...
3) Faders - Yep.....this is a group now. Fading wether they know it or not. the truely apathetic, in their heart know it is a pile of nonsense but go anyways because of family, class. Not eager to talk about anything "spiritual".
4) True believers - There are still some. People that had been in it forever. My mother for example. Her only regret in life besides her son leaving, is that she couldn't serve shoulder to shoulder with Christs brothers sooner in life. An attack on the GB is an attack on God to them, without them ever putting that together. EVERYTHING somehow relates back to the end, the new world or whatever. Plane crashes? Their families should know about seeing their loved ones again. I hope none of our brothers were on the plane. Gas prices down and economy on the rebound? The world is lulling people into a false sense of security. You can't win. Don't try.
5) Everyone else - Generally normal people giving over their minds. The congregation is a social structure, and they like it. Nothing wrong with that, and they probably won't bring up anything bioblically related because they aren't that interested.
On a side note, we have had lots of people visit us recently from other places in the world. ONLY when there is a lull in NORMAL conversation, is the default......so what the ministry like here.....or what did you think of last weeks WT? ONLY........when the conversation dies. Speaking about doctrine is simply impossible because only one viewpoint is allowed. ANY deviation from that viewpoint no matter how benign creates an uncomfortable conversation almost immediately.