Even many popular mods fuck this up! DEI in Total War Rome 2 needs submods to make the AI play by the same rules as the player!!! This is top of the most subscribed list right now FOR A REASON!!! https://steamcommunity.com/sharedfiles/filedetails/?id=36258...
Make the AI play by the exact same rules as the player. Make a scaling AI difficulty slider which goes from "piss easy" to "insane grandmaster" but without cheats. It's not that hard to do this, the chess engine crowd figured it out back in 2001. FEAR figured it out in 2004. Game AI has straight up not improved and at many times gotten worse in the ensuing two decades.
They really didn't. No one likes playing against weaker chess engines. They play perfectly like a higher-rated engine and then randomly make an obvious blunder. They don't play naturally like a human player of that rating.
The weaker AIs in Civ games do a far better job at "playing to lose" than low rated chess engines. It's not even close!