Lol, the MC is only as interesting as his interactions with the rest of the world are. So developing the other heroes through things like the untimely deaths of close friends is completely necessary and a sign of decent storytelling. I can't even imagine how boring this story would be if there was no human/demon conflict or no people from his world. It'd just be him being a merchant and denying the advances of the spider and the dragon.
@BestBoy that can still be interesting. In fact I thought this was going to be slow life type isekai. They started out with MC away from the big conflict. There are many good isekai of this type.
So when they pulled the war stuff with focus on the other heroes, I just can't take it seriously. And then after couple chapters, they went back to the MC and his fun slow life. Then go back to other heroes. Since my expectations have been the MC's slow life, I find the other heroes part to be distracting.
It would be better if they just keep focusing on MC up to the part where he got transported to the battlefield (or until he meets the other heroes if that's going to be the story). Then a brief flashback to the other heroes would be acceptable.