So where to put your investment dollars then
I spread mine out across many mutual funds in many asset classes (including two real estate funds). The idea is to not try to pick the industry that's going to do well. On the whole they average up over the years. I have over 30 of such mutual funds in equity asset classes (counting the high-yield bond fund as an equity fund even though it's technically not).
IMHO when you get near retirement put 25% of your money in mutual funds that are traditionally "safe" funds, again spread out across many asset classes (i.e. short-term corporate bonds, long-term corporate bonds, LT treasuries, ST treasuries, money markets).
The idea is that if you have a withdrawal strategy of 4% annually, and if you experience a huge stock market downturn where everything in equities is down, you have about 6 years worth of "safe" assets to withdraw from for the equities to go back up. And usually you don't need the safe funds anyway because in most stock market downturns there's usually some industries that are up anyway (i.e. in 2020 the tech and health care funds did well when most of every other equity classes went down).