Meetings are the linchpin of everything. If someone says you have an hour to investigate a company, I wouldn't look at the balance sheet. I'd watch their executive team in a meeting for an hour. If they are clear and focused and have the board on the edge of their seats, I'd say this is a good company worth investing in.
If the investor doesn't have enough time and skill to investigate individual stocks or enough money to diversify a portfolio, the right thing to do is to invest in exchange-traded funds that give you exposure to asset classes. It does make sense for the individual investor to think in terms of holding individual asset classes.