The difficulty setting in Civilization games has never been “how smart is the AI.” The AI always plays with the same level of “intelligence” (which is almost none). What the difficulty setting controls is how much the AI cheats (which is a ton at the highest levels) and how aggressive it is.

My problem with Civ 5 (as a player of the series since the beginning) is that they’ve added a ton of stuff to the game that doesn’t actually make it more interesting or challenging to play. At the same time, instead of improving the AI to make it more interesting and challenging to play against, they decided to hobble all of the strong strategies from the early games in a way that just makes the game more annoying to play.

The fun part of the Civ series has always been about building the largest, most technologically advanced empire and steamrolling all the AI’s cities. Since Civ 5 this has been flat out impossible due to the changes they made to the game which cause exponential corruption / waste for large empires and the inability to stack units which means large armies are extremely tedious to manage.