You are completely wrong. First of all because serfdom is something very other than slavery. Second because serfdom was limited to only certain parts of Europe. Third because serfdom did not immediately follow the disappearance of slavery.
Incorrect or misleading on all three counts. First, while slavery is not identical to serfdom, they both serve the same purpose: providing a source of forced labor to work the lands that provide the wealth for the rich and powerful. Second, whether "serfdom" was limited to only certain parts of Europe depends on how one defines the term. Third, the wealth of the elite in the Roman Empire was based on slavery, that of the elite in Medieval Europe was based on serfdom, and in between Europe suffered a collapse of civilization in which institutions like slavery and serfdom could not be maintained.
There has never been an agrarian civilization that was not founded on some form of forced labor. Slavery was the most common form but not universal. Slavery was actually
abolished in Europe, as opposed to being mostly, but not entirely, abandoned for a workable alternative, in the 19th century, slightly before it was abolished in America.
Now, how about those other social norms that were mentioned? You responded only with a flip falsehood.