A new kind of teshuvah, quite unlike its predecessors, has made its appearance in the last generation: the teshuvah of one completely outside the religious fold, to whom the entire pattern of observance, the yoke of the mitzvot, is foreign.
The halakhic term that best fits this new phenomenon is "an infant raised among gentiles."
This is not to say that ba'alei teshuvah of the new variety are subject to all the details of the laws that apply in that case, but that it aptly describes their spiritual state.
They are like captives, spiritual captives, among the gentiles, whether the latter be actual non-Jews or Jews who think, speak, and behave like non-Jews.
(Even in Israeli society there are many people who think of themselves as Jews, but whose way of life and outlook are indistinguishable, except in language and locale, from those of other peoples.)
The return of the "infant raised among gentiles" is in many ways, even according to halakhah, fundamentally different from the teshuvah described in the traditional literature.
The former, too, is a return, but not to some personal point of departure.
Rather, it is a return in a deeper sense, a return of the individual to his people, to his origins, to the crucible in which he was formed, both historically and morally—to God.
Judaism and the Jewish people welcome all who wish to come "home," from near and far.
But how much greater and more powerful is the act of one who returns to a home he never knew.
–Rabbi Adin Steinsaltz
From Teshuvah by Rabbi Adin Steinsaltz