Exactly. For example, if we live in a small town with a Walmart, and everyone buys most of their clothes there, our fashion culture in that town is that of Walmart.

As you say, we do not express Church activities in a cultural vacuum. Churches have no choice but to express themselves (to some degree) in the common culture of their day, even if they have a death grip on old traditions like Anglicans or Catholics. Church culture is not inherently wrong but becomes harmful when it becomes an obstacle to others discovering and knowing God.

All that said, executing a perfect church plan in a "moving-target" culture with imperfect people is the next big challenge. I'm not sure even Jesus has a miracle big enough to solve that problem. :-)