id agree to an extent with your second paragraph. I do believe that all religion, though we focus on the main ones because they draw the biggest numbers, are heavily attached to time and place. For whatever reason, more mainstream religion is tending to fade in Europe and to some extent in North America, imho because some of the more moderate stances dont really have a niche in contemporary society in those places. The Christian Church is growing very rapidly in some areas and denominations which are struggling in some areas, still have quite a hold on other long term regions of the globe.
All culture has to be able to respond and shape the changing timeperiods and milleus that it finds itself apart of. For whatever reason, some portions of Christianity arent doing that as effectively as others right now. That probably wont stay that way forever, but it will likely be the culture, not the religion that cause the change to something that is a little more moderate.