Level scaling doesn't necessarily mean "guaranteed challenges." It usually actually means "bland/samey gameplay."
Listen to what you're saying here. For this to actually be true, you're essentially saying that fighting opponents who have stats appropriate for your level (and modified for the difficulty intended) can only be described as bland. Because that's mainly what level-scaling is.
And that's simply ridiculous, because you can have a game that doesn't use level scaling, yet plays out exactly the same way assuming you run into encounters
*at the level for which they were designed*.
And if doing that results in a bland adventure, then someone has really dropped the ball and it has nothing to do with whether the game uses level scaling or not.
