How long can the index fund advice be sound as index funds are moving from following the market to making the market? The sheer magnitude of success of the var

How long can the index fund advice be sound as index funds are moving from following the market to making the market? The sheer magnitude of success of the various index funds that invest proportionally to the market cap of the top 500 stocks, in aggregate, could have the effect of perpetuating the status quo, masking indicators from non-index investor activity.