A warning from a man born half a millennium ago for those who think vague religiosity or spirituality is sufficient:

…they think that any zeal for religion, however preposterous, is sufficient. But they do not realize that true religion ought to be conformed to God’s will as to a universal rule; that God ever remains like himself, and is not a specter or phantasm to be transformed according to anyone’s whim.

John Calvin, Institutes of the Christian Religion, Vol. I, p. 49