why we can not Buy after a doji?

why we can not Buy after a doji?

readers message
———————
Hello sir
In many videos you mentioned that after a doji if price goes up and closes then sell stop order at close of doji, But you never said if a doji appears and closed below doji and Buy stop to Long the postion, why we can not Buy after a doji ? Thanks
———————

video here

if last bar close then count number of candlestick color continuation