If anything, the oldman put the siblings in danger due to the lack of understanding of their level and skill sets. The oldman dying was his own fault. Then again, seeing as how the ending was rushed, it was a force reconciliation event for the family.
I wouldn't say so. The siblings weren't carried through this by their skill but plot contrivance via the drops. They actually were completely outclassed for the random bullshit the dungeon threw at them. This is actually the one thing he had a real point on. The siblings had bumbled about through the dungeon making weird mistakes and assumptions whilst treating the whole thing as a game.
However, that makes all the more reason for him not to be revived. It would make the one actual lesson he had to teach, that they could actually die in these fights, stick. Yet, just as the conflicts are all nonsensical bullshit, the solutions are all nonsensical bullshit and it is again solved by a random dungeon drop.
I'm actually kinda happy to read this today. A few hours ago, the translation for a random isekai novel I was reading finished. It had a dumb name but an interesting setting. Rather than the usual expulsion and mockery of the mc, there was mass lay-offs as the country starts pushing automation and technological development leading to an exodus of adventurers. The side characters were also good but the mc's personality was terrible, like what an inconsistent idiot thinks being aloof is like. Fortunately, it's sudden ending was meant to lead into a sequel with a different mc. However, to get to the actual point, the mc spoiled the side characters and setting enough that I kinda hated it but then I read these chapters I realized that that story had potential that it couldn't utilize, that it was worthwhile. I realize because I saw that this story is an actual dumpster fire. Almost nothing anyone did made sense and there was nothing worth mentioning about the world itself. It might just be that I've seen a few things that are actually interesting lately, but I genuinely feel like this was a waste of time.