Are multivitamins worth taking if you eat reasonably well?

For most people eating a varied diet, no — large trials have generally not shown benefit for healthy adults, and some nutrients in excess carry their own risks. The exceptions worth taking seriously in India are specific rather than general: vitamin D deficiency is widespread even in sunny regions because of indoor lifestyles and clothing, B12 deficiency is common among vegetarians, and iron deficiency is very common in menstruating women. The sensible approach is testing for these specifically and correcting what is actually low, rather than a broad-spectrum tablet that addresses nothing in particular.