I find it interesting that he has the main conflict of wishing he weren't an old man at heart. If this is a story about him finding revitalization in a new life and role, that's arguably the best possible use of isekai, as much as it's a very worn premise at this point.
I mean compare that all the stories we see of isekai starring a young man getting cheat powers. Often the takeaway is "HAH! See now I belong to a world where I never have to grow or change as a person because I'm basically a demigod and people fall over to cater to me like I've always been entitled to!". Which I suspect is what people hate most about the genre, not so much the setup itself. It'd be like if Game of Thrones spawned legions of imitators and the protagonists of them were all different shades of Joffrey.
An old guy who yearns for healing, on the other hand? I can cheer for his search for energy and happiness because that's a struggle a lot of us have. However we get there or what common tropes we run through enroute, I want to see his smile.