Well, these days most of the isekai stories are harem gener. U can consider to continue, if the plot is good. Of course what I hate about harem is mc collecting girls like Pokemons and ignoring them after a few chapters. If everyone has proper reason to be with mc then it's okay with me.At the end of the day, it's fantasy world where strong have their own previlages. So there's no problem if mc wants more than one girl because he has the proper conditions. There is no reason to be bound by the so called values. (Of course there is no problem if mc prefers single gf). Even in modern world many rich people are not satisfied with one partner, not to say anything about that kind of world where the discrimination between higher and lower classes(fantasy world - weak and strong, real world - rich and poor) is more obvious.