Renaissance is part of the market, and it's the sort of thing that we individual investors can't beat. "The market can't be beat" doesn't mean no one can see better returns - it means a random yahoo like me simply can't compete with the information, processing power, and access funds like Renaissance have.
Thus, an average investor is a lot better off with an index fund instead of trying to pick individual stocks. (Funds like Renaissance's Medallion simply aren't available to people without tens of millions of dollars to throw around, too.)
Funds like Renaissance's have minimum investments in the millions, are often invite-only, etc. We average investors simply can't play in those leagues.
People have been saying that about rentech for the last 20 years. People have also been saying that about berkshire hathaway for the past half century. At some point, past performance IS indicative of future returns.
I'm not sure about any Rentec mutual fund, I don't think such a thing exists, but aren't the funds they have open to institutional investors not doing particularly well?
When most people say Rentec they think Medallion, which while being spectacularly profitable over 20+ years, is now a closed fund only open to current employees last I heard.
Thus, an average investor is a lot better off with an index fund instead of trying to pick individual stocks. (Funds like Renaissance's Medallion simply aren't available to people without tens of millions of dollars to throw around, too.)