There is actually a reason why it hasn't advanced and why they have to rebelled but it's a big spoiler. In my opinion the story is pretty good
ugrh you really need read it more couse your question is actually big major plot to the story any explanation to that is major spoiler.
please give it a second chance my dear
I feel you I was questioning the same thing while reading the story but after finishing after season 3 it all makes sense why there's no advancement that happens.
literally just started this but the fact that, given the title, after 66.666 YEARS the humanity didn't advance in technology or magic till he was reborn is so annoying. And the 12 gods? after this many years how come people weren't obligated to serve them- in case the MC is not just some crazy fool who wants to be the most powerful and actually has a reason as to why he wants to defeat them?
I would really appreciate it if you'd tell me if the story is worth it. should I act like only a couple of years(like 20) have passed? otherwise I don't think I'd be able to take this story seriously. It icks me too much even tho it's a stupid reason, I know