People said that this is overrated. While they are too simpleminded to see why it suddenly become popular.
tl;dr : The whole plot is funny meme joke
Most Japanese AMG has usual trope pattern where the story separate the seriousness of drama and funny moment in separate time. OP MC or Nakama Powah often becomes the plot armor.
But this is different, the seriously dramatic moment is cool but also... is actually hilarious joke even without funny moment at all.
Most story even like Overlord and Demon Lord Slave Magic have to put funny moment of self panic just to put joke, or even Gintama which just doing slapstick comedy for funny moment. So we can only laugh at that funny moment.
Meanwhile, The Eminence In Shadow approach new method where the MC and other character still serious but all of their action is (if you see thoroughly) actually a funny joke and memeable, although there are some funny slapstick too. Like no way everything is moving following his chuunibyou act and you are hailed as charismatic intelligent leader.
Another plus of this story, they don't focus on haremshit and ecchicrap just to please audience to not go away from story. They just keep make it as a joke such as the princess who found out that he is a con artist but doesn't know his true identity, a girl who think that he is galant warrior even thought that he is weak, and Cid doesn't even bat an eye to the harem he just made and think all of them as his soldier.
All of those rare traits that are a less usual in the time where Japanese AMG new idea is exhausted.