Now, to be clear, I'm generally against auto-scaling and am not a fan of it used willy nilly.
However, I think most people are missing half of the equation, and why it's such a difficult problem.
The problem with no scaling isn't so much that you might run into harder enemies. It's that if you grind a bit too much, or do some side quest out of order, entire sections of the game might be rendered too -easy-.
Again, imagine a game where there are, say, 5 quests that are good for your level 3 characters. No matter which you do first, now you're level 6 and the other 4 quests are too easy and become boring.
And if you only make 1 quest appropriate at any given time, your game is now too linear.
Appropriate scaling solutions attempt to fix this. But both no scaling and auto-scaling can be done very, very wrong. The answer, imo, needs to be somewhere in the middle where areas have the ability to scale to you, but don't constantly rescale (that is, no rats with dragon strength). But current quests, that i've never done before, should still be challenging even if I do them out of order. Areas that are 'hard' should never be scaled down, though.
For example, at the start of the game I have 5 quests available. The first one I do will be level 1 appropriate. Whichever I choose to do second will auto-scale to be for level 3 characters. Whichever I choose to do third will scale appropriately. However, that 5th mission is meant to be super hard, and will never scale below level 7 because it's supposed to be the last one I do. But again, none of this is easy. What if the player starts but doesn't finish each quest? They're leveling, but do quests get locked at the level the player entered? Or do they scale to present a current challenge? This is no easy problem to solve, and people acting as if 'no scaling' at all is the easy and obvious solution are missing the issues that too brings to the table.
No leveling has issues too. Autoscaling without complicated systems (rats as powerful as dragons) is the absolute worst, though.