That's not really true, if you dig deeper. Let's say top 50 stocks in SPX are correlated by around 40%, which means there will be a fair number of times when the stock and the market will go in the opposite direction.The popular stocks ARE the market. So might as well trade the index.
PS. If you really feel like you have good call on single names, you can trade conditional spreads on pairs of names. That adds another dimension to the kinds of views you can express
Sometimes it is easy to get carry away so the other poster's 1-2% makes sense for most of us most of the time.