Short answer
People making active decisions about health, serious about fitness or nutrition, planning a family, managing a relative's medication, or carrying a strong family history of a condition, get the most from testing.
Genetic information is most valuable when it meets a live decision. Four groups consistently get clear value: those optimising diet and training, couples thinking about children, adults managing ageing parents' long-term medication, and anyone with a family pattern of cancer, heart disease, or diabetes who wants to act earlier. If you fall outside these, testing can still inform, but the payoff is smaller.