I think that a lot comes down to personal knowledge and expertise. There's nothing wrong with investing in stamps, wines, coins or even third world farming, as long as you know enough about it.
For example, if someone has taken the time to become knowledgeable about Wilding Definitives (stamps) and they have studied the prices well enough to have bought and sold a few items, then it would be perfectly sensible if the right opportunity came along, to invest a sum of money in that area.
However, if some wideboy came along and starting shouting about how his Wilding Definitive Bond was the answer to everyone's investment worries, there was a minimum investment of £10k and returns were likely to exceed 500% in 3 years, then every sensible investor should run the proverbial mile, particularly if that particular wideboy had a history of making a lot of money for himself and losing a lot of money for investors.
Wine is a good example. This was touted as the modern El Dorado a few years ago by many dodgy advisers. Recently dozens of the investment companies involved have gone out of business, losing investors money. The dodgy advisers, no doubt, held onto their substantial fees and commissions. Wine didn't work for many investors but someone with the knowledge, space and money, can still have something valuable in their cellar.
I agree that, if someone does not have the knowledge or expertise to invest in a specialist area, there are funds that can help. The funds to go for though are those that have been around for several decades, those that are open and honest about current and past returns, and those that are regulated to an acceptable standard. Investing in fly-by-night funds has an inevitable consequence.