DOS-age:
1. run install.exe
2. run setup.exe
3. run game.exe
Config tweaking wasn't really necessary unless you needed to solve some memory issues.
INI and XML-tweaking are great for modding or adjusting a game to your liking. It shouldn't be and in most cases isn't necessary to edit those to run a game. You should only edit those to customize the game to your liking, for instance weather settings, AI-settings, etc. I agree with you when you say they don't have to be available in-game, though kudos to the devs who make them available in-game.
Even to this day you should be and most of the times are able to simply install a game, change the necessary settings (audio, video, controls all of which you can find in-game), start the game and play.
As far as those settings go, by default they should be based on the minimum requirements. Players should be able to easily adjust them.
I'm guessing the last time you checked settings, Watch Dogs wasn't released yet. There are plenty of threads, even some here, in which problems with WD have been reported. Problems caused by default settings which are plain wrong.
You can expect people to know how or where to change game engine settings. You can however expect that when you buy a new game for top bucks, it simply runs if your pc fits the minimum requirements.
If you want personalisable hardware, you buy a pc. If you want 13 in a dozen hardware, you buy a console.
If you want to buy a game with a console engine, you buy a console game.
