Do people here believe that constantly evolving theology is a necessary mark of the true Church?
No. I tend more to the traditionalist, or intentionalist, camp. I don't believe in a "living" Bible (or a "living" Constitution, for that matter). If something is living, it can be killed: up is down, left is right, white is black, slavery is freedom, evil is relative. Calls for institutional change, in my experience, usually originate from people who don't want to be limited by some aspect of the institution---sinners in this case---not those who are attempting to approve it. I don't see any modern prophets around, do you? Or theologians offering insight at the level of the Church Fathers. Only destroyers. Mankind tends to have a little too much hubris. I trust the Church Fathers. They were much closer to Christ and His divinity than I will ever hope to be.
I'd agree that the faith doesn't change, but that our feelings about it do. It's inevitable. But Orthodox Christianity has preserved for us eternal and unchanging aspirations which need no improvement. Any changing that is done is to be done by us---by me personally, internally.
In the last 50 years, under the influence of Saul Alinsky and his fellow travelers, half the Roman Catholic Church has evolved into what is, frankly, cheap crypto-Marxism. I don't regard that as an improvement, and it is killing their church. Their theology now wallows in the mud. I don't want to be fashionable with sinners; I want to be the best Christian I can be.