terrible way to manage investments. With all the uncertainty, gradual movements, underweighting or overweighting certain types of assets or investments, makes a lot more sense than going all in or all out, the vast majority of the time.

Unless you are very young and/or have a very long time horizon. In that case, being all in is pretty much always the way to go. But most wealth is concentrated in the hands of investors who aren't all that young or have all that long a horizon.