Game difficulty in games nowadays boil down to handholding easy or unfairly difficult.
By "unfair," they either increase enemy health, damage, or just intentionally make it based on luck because of poor game design. See OW2 PvE or GTA Online. Of course, that is to get you to "buy" your way to a victory.
I feel like strategy games are notorious for how bullshit they can get, at least at higher difficulties, with how much the AI gets to cheat. And it's a real shame, because while it
can make it more challenging and engaging, it also can make it total nonsense.
Vision blocked by fog of war? The AI can see the entire map, at all times, including hidden units.
Start with 1000 gold and a unit costs 100? The AI starts with 10000 and can pop out units every turn for free.
Your warrior has 10 attack? Well the AI's exact same (free) unit has 20 attack.
Not to mention how the gameplay can involve tipping points where every faction drops what they're doing and tries to dogpile the human player to stop them from winning. In some cases, like if you're close to victory in Civilization, it makes sense. But stuff like Realm Divide in Shogun 2 will take utterly loyal allies or vassals that have been at your side the whole game suddenly flip to hating you and trying to stab you in the guts. Total War: Warhammer will have factions march armies across the entire earth just to fuck with you, since you're the human.
Now, I get it. Making an intelligent AI for a strategy game is probably the hardest part, and saying you've got a very smart, adaptive computer opponent will probably sell less copies than just smacking elf titties on a "Play now, my lord!" advertisement. But it's sad to see what looks like the whole industry and players just shrug and say "Well, it's as good as it'll get." Stuff like Halo Wars 2 went out of its way to get help from pro players and shape the AI around popular and effective strategies, like rushes and turtling. And GalCiv 2 remains the only game where I've had the AI actually show how smart it was by saying "I see you amassing troops on my border, but since you're at a lower difficulty, I'm prevented from acting. But I
know." I feel like people just accepted mediocre AIs with unfair cheats as the only way to add more difficulty to strategy games. If anything, the AI should be brutally smart, and
you get cheats on the easier difficulties, with the hardest mode being fighting it on an even playing field.