The fun of the game comes from the surprise, from being on the edge of your ability and mastery.
Once you've learned a dominant strategy in the game that always works, it becomes boring, a chore.
All of the discovery is gone.
All that's left is the monotonous effort.
At the beginning of your career it's a thrill to figure out how to navigate organizations to make things happen--yes, it's a treadmill making it hard to make forward progress, but you can take the thrill and the challenge of achieving it.
But once you learn how to navigate it well and resiliently, all that's left is how hard you have to work to counteract the treadmill to make anything interesting happen.