Wow. I can't believe this author just ruined his story like that. I fundamentally despise when an author takes the unique premise it sets up and then undermines it entirely. What was the point of making him a decrepit old man if he's just alright now? Him being physically useless but wise while training the next generation of adventurers was a story worth telling. It gives him a central goal, creates a proper end flag for the series, and has emotional weight.
Whatever fuck it, dropped. I'm so sick of bad isekai stories when there are so many good isekai web novel's left unadapted.