Yes, beta is the overwhelming source of returns. I was referring to factors in the sense of the University of Chicago research on market inefficiencies (where momentum is the strongest factor for inefficiency).

If you buy a “factor-weighted” etf the idea is it’s tilting you into those “factors” away from pure beta like buying whole market.

PE you could argue is largely just leverage plus an illiquidity factor play, since if PE just returned beta (which these days it might!) you’d be smarter to buy the S&P500 with equivalent leverage and not pay crazy fees.