No,you can lower the difficulty in Skyrim or RDR2 and it's still not low effort or instantly rewarding. You can up or down the difficulty in Uncharted or Diablo but it never adds complexity. The Witcher 3 is this sprawling, massive and complex game but you can play it for a short time and still get rewarded and you don't have to put in much effort at all cause the combat and systems are all so straight forward and easy without loosing complexity. Compare this to Skyrim and you can play for an hour and litterally get no conclusion or reward to anything you attempt.
I disagree with almost everything you've said here.
For starters, how does one define what is and isn't rewarding to the player? For some, it may be discovering new places on a map. It may be getting a powerful new item. Completing a story quest. Leveling up. Getting to the next cutscene. Experimenting with game mechanics. Meeting, and befriending new characters. Taking screenshots in a beautiful environment. I could go on all day. Literally any number of things may be rewarding to any number of people, so if you're going to make the general assertion that some of these games aren't rewarding (be it in short play sessions or otherwise), I'm here to tell you that you're wrong.