Where I say:
"the overall function of religion is uniform."
I mean its general function of social regulation, social pacification, and social organization.
Where I say:
"[Christianity's] respective functions [in the respective eras] bear little resemblance to one another"
I'm referring to the specific pattern by which it achieves the general function and the dimensions within which it's called upon to do so.
Religion changes its hymns to suit the tastes of time. It's mission is to reach souls in the state it finds them in. I generally think it healthy for religion and secularism to be in a state of creative tension, in a civil society. The relatively absolute trimuph of one or the other, leads to subpar outcomes.