I think it's more than "a few". For one thing, many 401k-equivalent funds that government employees can make contributions to are low cost index funds, and there are lots of government employees. For another thing, most 401ks offered by large corporations also offer low cost index funds, which many employees contribute to because they're usually the default that you get if you don't pick something else, and there are lots of employees of large corporations.

Nothing can protect you from ill timed trades.

However, trades can only be ill timed if they are made. If you just pick an index fund with an appropriate time horizon for your planned retirement and then leave it alone, you don't have to worry about ill timed trades because you aren't making any trades at all.