> slavery or something similar (serfdom etc.)
Serfdom is very different from slavery. Even slavery is not always as bad as Roman slavery.
Roman slaves could be legally killed, tortured and raped (even children). Serfs might not have fair access to the law but at least in theory they had recourse and society recognised mistreating them was immoral.
Serfs could (meaningfully) marry. They were tied to the land so could not be separated from their families and sold elsewhere.
"Serfdom is very different from slavery."
And Mac is very different from a PC, but they are still personal computers that pack some computing power...
My wider point was about unfree labor in pre-industrial conditions. There were many serf uprisings in Central Europe, which indicates that being a serf was sometimes very hard to bear.
We are so used to free labor nowadays that we can't really imagine a world where the vast majority of the population is physically subjugated to some lords.
My point is that Roman slavery was a lot more brutal than what was required by the lack of technology.
I beeeive (I cannot find hard data, although things like the Doomsday book should have recorded some snapshots of it) while there was a large serf population, it was not the "vast majority" as there were also lots of free peasants.
Yes, it was a hard life, but far better than their equivalents would have suffered under Roman rule.