Wicca is explicitly a modern religion, being the brainchild of Gerald Gardner during the 1950's in England. Wicca is however heavily inspired by, and partially based upon the true ancient ways. If you look into Wicca you will find parts of it clearly inspired by the Celts, Ceremonial Magicians, Norse and Greek mythos and folk beliefs all over Europe. However Wicca is not the religion of the Celts, Norse etc, it is only based upon their ways but has slightly different interpretations. For example the Celts have the same 8 solar holidays as Wicca does. However, in Wicca all 8 are of equal value, but the Celts interpreted the days a little differently, and considered only 4 of them to be major events.

Wicca is a beautiful rebirth of ancient ideals, merging together pieces of history with modern views.

For those who firmly believe I am totally out in left field, I quote Scott Cunningham, from "Wicca: a guide for the solitary practitioner" Glossary entry for Wicca:

Wicca: A contemporary Pagan religion with spiritual roots in Shamanism and the earliest expressions of reverence for nature. Among it's major motifs are: reverence for the Goddess and God; reincarnation; magic; ritual observances of the Full moon, astronomical and agricultural phenomena; ...