Isekai, timetravel/transmigration and system -- all in one!
The supporting characters are nothing more than foils for the OP MC and get stupendously tiring. 40+ chapters in and my levels of caring are dropping rapidly. The MC isn't a strong enough character to carry the story, so I'm not sure I'll keep reading it -- might binge it at some point since it is an isekai after all. I don't understand any of the characters motivations or roles, but I'm guessing there's some reveal regarding at least the MC later in the story (something to do with lost companions has been hinted). For a 'mystery' it's pretty weak -- I'm not all that interesting in even finding out since there isn't a clear central conflict to begin with. Without some kind of antagonist (even in the abstract) the story feels kind of meandering rather than mysterious.
I'm guessing the high ratings come from the RPG focused narrative, but the plot is pretty weak and the system doesn't seem particularly consistent or rule based. It's 'fair' in my opinion, better than 'average' but not 'good'.