The honest summary of sixty years of research: nobody times the bottom — professionals included. But "you can't time it" does not mean "timing doesn't matter". Four things do come out of the data:
Buying below a company's own historical valuation earned more on average; waiting for "truly cheap" cost more return than it saved (time in the market beats timing the market).
Buying while the price sits above its 200-day average historically delivered similar returns with smaller drawdowns (Faber 2007).
Entering in parts (say three tranches over three months) removes the emotion and the bad luck of a single moment.
Scaling positions to volatility historically improved return per unit of risk (Moreira & Muir 2017).
And the biggest documented trap: buying at peak attention. Stocks suddenly in the news everywhere went on to lag on average (Barber & Odean 2008).