That's not exactly representative of the market as a whole and does not change the fact that most investors have lost money as of late.
Nobody I know recommends investing "in the market as a whole". With good advice, there are literally hundreds of stocks, indexes, ETFs and mutual funds which are up substantially (100% - 700%) over the past eight years.
If you bought stocks 8 years ago which were brilliant investment ideas then and are down now, buy more.