Level scaling isn't inherently bad, and in open world games it's even necessary. I'll even go further and say that while the level scaling in Oblivion was gamebreakingly bad, the level scaling in Skyrim was pretty good.
I'm fine with some areas being gated off by very strong enemies. Exploring, running away and coming back later is fun, but alternating between trivial and overwhelming challenges because you didn't explore the locations in the right order is not. A game that allows you to go wherever you want needs some way to dynamically adjust the difficulty and a combat system with a good balance between character stats and player skill. Many games screw up the latter and make enemies that are two or three levels above you unbeatable.
That's the problem with Skyrim. The entire combat system is too dependent on stats and leaves very little room for timing or tactics which makes the scaling fat too obvious.
I don't think it's inherently bad, but it's maybe a little lazy, and it's definitely not necessary. What you're getting at here is one or both of two issues that any game needs to address: Guiding the player to challenges suited to her and her character's abilities, and communicating the challenge level to the player (and perhaps also the reward for success or penalty for failure) before she commits to facing it. If the player encounters too many challenges that are either trivial or overwhelming - nevermind yo-yoing between the two - the game has been poorly designed.
One method of "gatekeeping" is some kind of in-game "key" that a player needs to find, earn or build before moving on to more challenging regions. In
Subnautica, there's no character-progression, the player's capacity to handle the challenges is all based on the equipment she crafts. Vehicles are rated for dive depth, and greater dangers lurk in deeper waters. The game is open-world, and you're allowed to swim into waters you're unequipped for, and you can drive your minisub into depths that will crush it.
Another method of guiding the player to appropriate challenges is the "conning" you get in MMOs. The game visually displays the challenge presented by a potential adversary. It's a bit heavy-handed, and the visuals can be intrusive, but it gives the player the information she needs and lets her choose whether to bite off more than she can chew.
Finally, some games -
The Long Dark and
Far Cry Primal are the examples I've chosen - leave it up to the player to learn the environment (that's the core of any exploration game, obviously). Both of those games rely on the player starting out with some real-world knowledge, that a grizzly bear and a sabertooth tiger are dangerous and deer are a good source of food, and then figuring out the animal's behavior and their character's capabilities within the game.
Subnautica needs to help the player more, because the whole point of the game is that it's another world. Even so, the predators kind of look toothy and threatening, and when you wander into a dangerous zone early in the game, your character's in-game computer says something like "Leviathan-class fauna detected." Games with lots of different adversaries may need to help the player catalogue and remember things as they go -
The Long Dark has only 5, real-world animals, so it's not a chore to distinguish a rabbit from a wolf and remember their behaviors. A game set in a more complex and alien 'biosphere' needs to help the player more than that. Deciding whether the character would know more about the world than the player does is important, too. In
Subnautica, your character has crash-landed on an unexplored alien planet, and is just as lost as the player is, and the game proceeds accordingly, but provides with a handheld scanner and portable computer to learn about the animals and record the information for later reference.
Skyrim has so few meaningful differences between races and classes that I don't feel tempted to replay the game at all, I''ll just finish the interesting parts with my one character and then scratch it.
