It is the opposite. Market timing does not work reliably. Active management produces worse results on the long run. no individual trader or active manager can consistently beat the market. however active fonds may have periods (even several years) where they out perform.

for private investors buy-and-hold of highly distributed ETFs is the best way to do it. The easiest way to get started is a one ETF portfolio like e. g. Vanguard FTSE All World or SPDR MSCI ACWI IMI. They perform internal rebalancing automatically and you virtually have nothing to do. buy them and don't look at them for the next 20 years.