There are certain fashions of thought, as others have pointed out on this website in relation to other phenomena (e.g., the rise of Islam in the West). I think it would be naive to discount that entirely when it comes to the rise in agnosticism. It seems, bizarrely, that many people think it more "open-minded" to not belong to any religion and just be a good person, because after all with so many religions (and even so many different forms of what the religiously-illiterate popular media call the same religion, such that tambourine-shaking, snake-handling Baptists and Orthodox Christians seem to be presented as though they are on equal footing), it's a bit arrogant -- so the claim goes -- to say that one is right and the others can't possibly be. So, in the interest of being as tolerant and open-minded as possible, many people find it easier to give up any strong conviction in favor of bland pietism and the "social gospel".
This isn't just a young person's game, either. My grandmother, who is otherwise very pleasant, reacted quite negatively to my renewed/maturing interest in religion in my early 20s, saying that she couldn't understand why anyone would bother with it when "all they do is tell you what to do". An understandable idea, perhaps, for someone who knows only Western Christianity (her family was Greenlandic Danish, so I'm assuming there were some Lutherans in there at some point), but that's all the more reason we should be working to bring such people (and there are millions upon millions here in the West) to Orthodoxy...
