Ask Gary Smith, Curtis Arnold, some of Larry Williams systems, Vilar Kelly, Richard Saidenberg, Peter Ann, R.S of Houston they were massively oversold and for handful of years they did not work at all, guys in the pits made sure of that. I bought many systems in 1990s to 2006, I found several that I liked and they traded together, but I do much different, I wait for huge drawdowns then they kick in till making new equity highs and then that system(s) shut down.
If a system is very good, no sense to sell it, dealing with the public for me was never fun.