Yeah so nearly everything you say is wrong after the first half sentence.
First: It doesn’t take a long time to civilize someone that can actually well be done in one generation. Of course that is if you really just want to give them a start with better rules while respecting their heritage. If you mean with „civilize“ to forcefully erase their heritage and replace it with your shitty racist version than yeah that doesn’t work.
Second: The term barbarian is lightly said by you and others of you ilk while good old Julius would think you are barbarians for not admitting that he is you emperor or such things.
It is indicated that the norther Europeans had quite the well developed culture (with women rights no less) they were but lacking in military might and connectivity between their tribes
Third: Christianity was always used as an excuse to torture non Believers and rob people of their land. I find it highly distasteful that some of the catholic saints were then what isis leaders are now. There was culture before and for most of it Christianity just made it worse especially for women and foreigners.
Fourth: aristocracy and feudalism are so inefficient that they could not on any account help or even control our current civilization
To sum it up: I am pretty sure even hundreds of years back there were poc who were more civilized than you are now