That's not a helpful way of looking at things since individuals do not trade the average strategy. They trade whatever theory they are seeking to validate, which is too often "their gut" or the latest technical analysis woo. These people are cannon fodder for algorithmic traders and market makers. The average of all retail trader strategies is definitely not the market.
no, most strategies necessarily will be losers if not near the efficient frontier. trades average out to the market.
the parent, maybe mistakenly, stated any strategy will have average returns, but consider the naive strategy of putting all of your money in a small number of (often highly correlated) stocks. that trading strategy will underperform the market on average.
