The market's shift from active management to passive management has significantly contributed to an 18-month rally in stocks. However, experts caution that market structure can work both ways, potentially leading to downturns as well. David Rosenberg warns that the massive bull market in passive investing could end poorly for boomers who do not rebalance their portfolios. Additionally, products generating high yields and trailing total returns have seen $30 billion in inflows over the past year, raising concerns about their performance relative to the index. The rise of 'Boomer Candy' products, gimmicky ETFs chasing the dumb dollar, and the increasing interest in investing among young people are notable trends in the current market landscape.