Generally speaking, beings anywhere in the universe don't usually change unless they have no other choice. Though this dynamic has a group effect let us look at the changes first on an individual being.
Most beings are creatures of habit. And habits, all of them, are not easily changed without consequences, sometimes severe in nature.
And this so far is only one individual being. Now we take changes for example to a human family. Let's say this family is Republican and Catholic and American Northern East Coast and has been this way ever since they moved from Europe in 1785. No long term friendly contact has been allowed in any personal way with this family unless they too were Republican and Catholic.
Let's say, for example, the daughter of this family decides to go to a public university today in 2008-2009. And she meets a young man who is not Republican and not Catholic and she decides she is in love with him and decides to live with him with the idea of marrying him.
Since her family is traditional Republican Catholic she is ostracized from her family and not spoken to again by her family. Though she is not excommunicated from her church for this she is shunned by her church and all her family. Her mother starts drinking and her father is so upset he starts having affairs with other women. Her mother finds out and kills herself. The father in dismay starts drinking and loses his career. Now he is on the streets with other drunks. It goes on and on.
Was the daughter wrong to go to a public university and live with a non republican and non catholic? No. That is not the point. The point is how fragile many families, systems of behavior and the very fabric of society is worldwide.
Therefore, if you were an advanced culture from another planet and you looked at earth like a beautiful quaint park in space that you could visit and your own civilization was about 1,000,000 years old and you naturally understood just how precious and how quaint a world civilization like earth is, would you want to destabilize and to change it so all this quaintness and preciousness was lost? No. You wouldn't. You would want to study how all these systems and individuals internally and externally worked and how all these lessons could be applied to your 1,000,000 year civilization that spans thousands of solar systems and thousands of inhabited planets throughout our galaxy.
So, in the end, the quaintness of earth would be what you would want to preserve if for no other reason than to learn from all interactions on earth and how they could help your own cultures survive better and longer.
In the meantime many vacationers and researchers from throughout your Galactic civilization would come to earth in disguise and interact with the humans here. If any of the people here suspected anything there is not much they could do about it because they are such an archaic system that they would be like deer to humans in comparison.
And just like deer and Bear in parks life would go on just like it does now.