If your timing is bad, the returns from an index fund are terrible. The best advice is not just to hold for a long period (25+ years) but also not to go all in or all out.
Returns are only bad on index funds if you pull out. Historically you're getting 7% over 10 years with virtually no fees. Managed funds rarely beat 7% and have fees which reduce any gains you may have made. Better to self manage and get that consistent growth.
