It's all down to experience isn't it. The negatively vocal Y's don't believe the baby boomers or Gen Xers that it will work out in the wash over time. Look at the Great Depression, that generation gave us the baby boomers. The baby boomers have had the big oil spikes and associated stagflation in the 1970's and still got on with it. Gen X'ers (and all prev generations still with us) had to deal with recessions in the 1980's, 1990's and most recently 2001/2002 bear market. There are economic and geopolitical events such as wars that are such regular occurrences in one's lifetime that all generations have to deal with.
Some of the poor vocal negative Y's haven't the personal history to reflect and place things in a constructive framework for investing and managing risk. Hopefully for them they will realise its an imperfect world and all you can do is follow an investment plan that allows for such imperfection. Some people never realise it...some too late. The lucky ones are the ones who dip a toe in the water. don't over extend themselves and are patient. If they give themselves time, and use that time to develop knowledge and skills, they can make money in most investment climates.
Cheers
Shane