This quote is always taken out of context. It originally wasn’t supposed to be about how people are “stupefied” by religion, it was supposed to be a direct comparison of how Tsarist Russia used the Orthodox religion as a method of control, in the same way that the British used opium as a method of control over China.

It was supposed to be a commentary about state power in a specific time and place, not a condemnation of religion in general.