True, but I can imagine a world where AI DMs are in vogue, and are curated not for their one-size-fits-all perfection, but for their aesthetic or functional qualities. The hardest thing to capture will be truly surprising off-screen storytelling moments that role playing games enable. Otherwise, you can probably optimize for 'challenging combat,' 'fun puzzles,' 'social interaction' etc...

Have a hard-nosed, Old School Revival (OSR) group who enjoys hack and slash dungeon crawls? Great, all you need is an AI who picks hard but fair challenges, describes dire and interesting settings, and keeps rewarding moments (in this case, hard-fought victories) coming frequently.

Like to tell stories instead? Seed a plot with a laid-back AI who leaves lots of room to breathe, throws lots of skill checks at crafty players, and excels at creating complex personalities and interactions via a cast of interesting NPCs.

Rimworld is an simulation/tactics/base-building game that offers more traditionally game oriented "AI Directors," but the different kinds of directors offer different prioritization over moments of peace, intense challenge, battle, etc., based on just a few settings. Even blowing out that settings list a bit more could create interesting results.