Answered this earlier,
A program is only as good as the programmer behind it, who is again a human. If you try to trade high frequency or other such strategies where latency (faster spotting the trade and execution) is important, you’d definitely lose out to a program. But if not, manual trading still works and will maybe continue working for a while.
That said, even before computers and programs, all manual strategies also had the same issue of not working with time as more people adopted it. This business of trading is extremely competitive and people go to great lengths to get an edge over others - with or without computers.