I started playing Company of Heroes 2 on Hard. I think Hard.
It's HARD.
As a kid I spent a huge amount of my childhood playing RTS games, but I always played them on easier difficulties and was, frankly, a smoothbrain. It was more about buliding my base and parading my army around and i would have been happier with a city-builder, probably, if I was familiar with that genre back then (something like Anno).
With difficulty it's never smooth. It just goes from "I'm blowing this out of the water" to "FUCK FUCK FUCK" when you first up the difficulty. With COH2 I got to where I could quickly bottle the enemy up.
Well, you bump it to Hard and it's not just resources (though I'm sure it cheats, RTS games always do), it legitimately fights differently. It uses abilities, it uses combined arms, it places machine guns RIGHT ON THE CENTRAL OBJECTIVE WHERE I CAN'T DISLODGE IT and then pounds me with mortar fire when I try to dislodge the machine gun and it overruns me with flamethrowers and it breaks off fights to live another day.
It's like having an actual person now. So far in my attempts (playing Soviet vs Soviet to learn to cope, symmetrical unit rosters) what happens is I do somewhat okay, at some point get pushed off the middle point, then get suckered into an endless fruitless fight that will at some point end in a catastrophic crumpling of my defense and the killing of all my squads.
I finally took to heart the importance of hotkeys, too. It's not that it's mentally taxing or even that micro intensive, but you do need to save a bit of time when the AI actively moves around.