Things in my opinion are not that complicated. The market valuations drive future gains. Being an investor for the long run always pays off. Only 20 pct of active “progessional” money managers beat the market. So right there passive investing puts one in the top 20 pct. Yes, in a down market one may temporarily lose money. But regular investment make a down market especially attractive for long term investor. Asset allocation and rebalancing twice a year should ensure investor has eggs in more than one basket to avoid egg in the face.
Since us market index funds r market cap weighted one can have his individual stock portfolio over weighed on value stocks especially in sectors that r underrepresented in the mkt index.