@dudewithmagic There's lots of common tropes that pop up in isekai MCs that I feel are unrealistic.
1. Slavery - Like you said, the MC in isekai always seem to be perfectly fine with slavery. I've seen several where they give some lip service such as "I need a slave to help me get by in this world" and then immediately go straight to the sex slave section to buy the most attractive woman they can find.
2. Adventurer's Guild - the world is full of demons and monsters and is pretty dangerous yet the first thought that passes through their minds is to join the adventurers guild. Being an adventurer is a very dangerous job that risks serious injury and death and despite that the MCs, who were previously from modern day japan and probably never got in a fight before seem to have no problems joining what is essentially a global mercenary organization to risk their lives for money.
3. Killing - despite being "ordinary high school students", many of them seem to have little to no problem killing other humans. That's just not realistic. Humans who kill other humans usually face psychological trauma from the event and require counseling. There's a reason soldiers (and others who are around a lot of death) suffer from PTSD.
4. Culture Shock - The MC suddenly finds himself teleported to another world. He has no family, no friends, and is forced to live in a completely different culture from what he's used to. Surprisingly, the only effect this has on the MC is that he misses eating rice and taking baths.
The MC should be suffering from great psychological trauma from the extreme isolation and constant life or death battles.