Yes, the slave trope is generic and morally bad, but at least it leads to a nice meta gag, when he meets another migrated hero from earth. Similar unique like truck kun and the horses at start.
What annoys me more: as so often, the leveling speed math is wrong.
It would not be just 20*20.
As the attributes from his multiple jobs stack, it should be much more.
He can not only kill stronger monsters and faster, thus increasing his leveling speed, some jobs give alternative, additional means of XP income that also profit massively from his power and multiply his XP income.
So it should be more like 20*20*X. And X grows over time, as he gets more secondary jobs. Given some time, he would level 10000 times faster than normal. 100 years of normal leveling in just 4 days. After a year he would have maxed out every existing job.