It's a complete misconception that "real AI" needs to be super hard. Give it realistic constraints like slow reaction times or noisy input. You can handicap it in many ways to control the difficulty. Modern chess engines can easily beat even the best players in the world. But by limiting the number of moves they search, you can set one up that new players can beat.
My favorite game AI is from age of empires 2. All other RTSes just let the AI cheat like crazy to provide challenge. For AoE2 they went to a lot of work to design an expert system and a custom scripting language for it. Tons of features were implemented to make it easy to write relatively sophisticated AI strategies. And they documented it well and made it easy for modders to write even better AI scripts.
As a result the AI on hardest can beat all but skilled competitive players without cheating at all (at least the current AI shipped with the steam version.) It's actually fun to play against and isn't a terrible substitute for a real human player.
Allow me to introduce you to a developer named https://en.wikipedia.org/wiki/FromSoftware ...
Although I understand Souls doesn't have permadeath, therefore it's probably only half the fun of Nethack.
__________
But Original DnD is where my inspiration-knowledge stops
Reach a point where all core problems are solved, and then create your own problems (and try to solve them).
Its just DF community that claimed it as their mantra, and their primary marketing of the game. But all sim games (d)evolve to this.
Kinda like Lucky Strike's "it's toasted!" slogan
I agree that if you have no way to measure that progress/improvement then the fun is lost.