Vitamin D is vital for your health. If you lead a healthy lifestyle, eat a healthy diet and from time to time, your skin is exposed to the sun, your body will manufacture the necessary vitamin D.
However, additionally taking vitamin D supplements will not improve your health. Vitamin D supplements do not improve cardiovascular health, protect you from cancer, or improve your bone health. Vitamin D supplements do not lead to fewer deaths, in other words, vitamin D supplements do not lead to less mortality.
Two huge clinical trials, where thousands and thousands of middle-aged and older men and women were randomized to vitamin D supplements or placebo, and had been followed for years, show these results.

Apart from a few, special medical exceptions: For the vast majority of us: There is no escape. If you take vitamin D supplements, your health will not improve. There is no easy and fast substitute for a healthy lifestyle. You cannot “buy” a healthy body with vitamin D supplements.