This could come by way of an investment adviser, or by investing their savings in managed, diversified retail investment vehicles such as mutual funds. The challenge posed by this approach is that it can be costly, since individuals outside a pension plan have to purchase investment advice and ongoing funds management retail, not wholesale.
Moreover there are structures in place that are deliberately designed to lessen systematically the differences in outcomes which might otherwise occur. Opinions will differ about how effective these have been, and about how effective they should be – as recent political events have probably demonstrated.