You could.. as the author.. NOT put them in sad, desperate situations to begin with if you didn't want them there.
Unless it's completely, undeniably integral that they learn something that will absolutely be needed in some way, and CAN'T be taught literally in any other way, (which I bet I could find a multitude of other ways.) I don't see the point.
No, actually I do agree with you. I do see the good points in the discussions.
This:
"to show the fragility of human beings and how we think our life will never end, and when death finally comes, we realize the fragility of our existences and reincarnation becomes this beautiful hope, a dream come true."
That's a good reason. If written well. I do listen. It's a beautiful reason to write about death.
My rebuttal to it though, would be:
Having the MC have a friend throughout a few chapters, 10.. 15.. 100 chapters, whatever number. and writing that characters death will still have that same impact of "fragility.", people are "fragile." People CAN die. Same thing.
Just because you have no concrete solution to explain 'why any story would be better WITHOUT an isekai', doesn't mean I'm a brick wall. It just means you have a limited imagination.. Isekai can mean a lot of things when it comes to story, and have a diverse list of characters, and sceneries. The death at the beginning, you so proudly claim to hold dear, can be shown in many other ways WITHOUT being transferred to another world chapter one.
Your turn.
Ayo? That's something new. (Especially to this discussion thread.)
Why didn't you just start off with the story about the wolf spirit?
What was so important to show them as an old person prior? (Not to ask you to spoil the story also which of the four would that title be?)

but I'm not fatigued.
I want to discuss why have the isekai at all. (The actual PHYSICAL jump from one realm to another, by death, warp, transmutation circle, magical school bus, or whatever reason.) Why isekai?
Isekai is the butt end of literally any other genre. the only thing that makes an isekai an isekai is literally: "i went to another world because (typically) i died." Why the extra steps to write something else?