To make a determination like that would require a very narrow definition of what it means to be religious, one which would necessarily exclude large bands of the spectrum of human experience that has been considered religious.
Critics of religion focus on a particular form of religiosity, one that’s easy to characterize and identify, to the extent that people who experience religious sentiments but can’t identify with this prevailing simplistic understanding of what it means to be religious find themselves struggling for new terminology. Nowadays, someone like this is likely to say “I’m not religious, but I am spiritual”. More often than not, this is an attempt to distance oneself from the forms of religion currently being held up for ridicule.
This unnuanced understanding of religion is rather recent. Einstein wrote quite a lot about religion, and it’s obvious that he applied the term broadly and made allowance for many levels of religion:
“The Jewish scriptures admirably illustrate the development from the religion of fear to moral religion, a development continued in the New Testament. The religions of all civilized peoples, especially the peoples of the Orient, are primarily moral religions. The development from a religion of fear to moral religion is a great step in peoples’ lives. And yet, that primitive religions are based entirely on fear and the religions of civilized peoples purely on morality is a prejudice against which we must be on our guard. The truth is that all religions are a varying blend of both types, with this differentiation: that on the higher levels of social life the religion of morality predominates.
“Common to all these types is the anthropomorphic character of their conception of God. In general, only individuals of exceptional endowments, and exceptionally high-minded communities, rise to any considerable extent above this level. But there is a third stage of religious experience which belongs to all of them, even though it is rarely found in a pure form: I shall call it cosmic religious feeling. It is very difficult to elucidate this feeling to anyone who is entirely without it, especially as there is no anthropomorphic conception of God corresponding to it.
“The individual feels the futility of human desires and aims and the sublimity and marvelous order which reveal themselves both in nature and in the world of thought. Individual existence impresses him as a sort of prison and he wants to experience the universe as a single significant whole. The beginnings of cosmic religious feeling already appear at an early stage of development, e.g., in many of the Psalms of David and in some of the Prophets. Buddhism, as we have learned especially from the wonderful writings of Schopenhauer, contains a much stronger element of this.
“The religious geniuses of all ages have been distinguished by this kind of religious feeling, which knows no dogma and no God conceived in man’s image; so that there can be no church whose central teachings are based on it. Hence it is precisely among the heretics of every age that we find men who were filled with this highest kind of religious feeling and were in many cases regarded by their contemporaries as atheists, sometimes also as saints. Looked at in this light, men like Democritus, Francis of Assisi, and Spinoza are closely akin to one another.”
Of himself, he said, ”“I am a deeply religious nonbeliever. This is a somewhat new kind of religion.”
So, exactly what are we talking about when we use the term religiosity in this question? All of the above?