"Theology is not about angels dancing in pinheads ..."

True. On the other hand, plenty of pinheads study theology. I know because I've often been accused of being one. 😉

I won't get down in the weeds on your conversation with LG, but I will observe that in the time frame you're discussing (between the Apostolic Age and Trent) there were 18 ecumenical councils, and nearly all of them were called in response to some sort of crisis of either theology or politics -- or both.

This was the era of local churches going decades without the benefit of communion with other local churches or the Church Universal. Considering the circumstances, the wonder is that there wasn't more divergence on theological development than there actually was -- which, logic says, must have been plenty.

Thus the need for the councils in the first place.