There's nothing wrong with isekai, and originality isn't necessary to make a story good.
The issue is there are a lot of bad authors. I guess you could argue there is too much demand for isekai, but not enough competent authors to write them.
MC is trash anyway, so I don't know why he's complaining. He let bandits go after defeating them, even healing them back up. I wonder how many people those bandits have killed and will kill.
I know in some Japanese manga/anime, characters have held up fingers while vaguely saying "it will cost this much", and the fingers represent multiples of ten thousand (Japanese and Korean are ten thousand based unlike English which is one thousand based). I'm thinking it refers to 700 x 10000...
@Keimichi The logic breaks down before that point. He said he could have survived drinking poison if he was a knight, but so what? Would they just have let him go after he drank the poison and survived? They ended up chopping his head off anyway, which I don't think a knight can survive either.