You’re right in that most video games give us that illusion. Yes.
But even when a game is selected to be on easy. The difficulty is still going to scale between say the first boss of the game and the end boss.
The developers of a video game usually have an idea of what level they want you to be by the time you get to the last boss to speak. And will adjust their difficulty to meet that expectation. Hell a lot of them will even straight up tell you “recommended level” for a quest that usually doesn’t get altered by selecting different difficulty.
Not to get off topic. But that’s what makes the Delves all Faction teams so frustrating. The end gamers don’t know what metaphorical “level” they are supposed to be on to have success in the Delves. And to be honest, neither do the devs it appears.
Back to what you were saying though.
To a certain degree a player does choose the difficulty by selecting what team scores to face.
A defense that’s two times the score of what your score is will be much more difficult than a team score that matches yours. Of course it’s not that black and white in GoW. What troops or hero weapons/classes are on the team matters a lot as well.
It’s not a miss if they meant to “miss it”.