What excites me about the way The Witcher 3 is being described so far is that it is reminiscent of Morrowind over Oblivion and Skyrim, with the strengths of the last two Witcher games. I mean, if it delivers premise, The Witcher 3 is almost exactly the kind of RPG game I've been lusting for years.
For me the role playing genre by definition is defined by diversity and causality. And a big part of both those tropes are the ideas that go beyond your player, but instead how the world around you is presented, your means of exploration, the struggles, the characters, and the way it changes. One of the biggest flaws of Oblivion and Skyrim that hinder my enjoyment is that the game world itself is heavily streamlined and diluted. Diversity is there, but that diversity panders to whatever state your player character is, or the style you chose to play. There's no sense of a reactive world, or a defined world that exists with or without your presence. What you end up with is essentially a big dull sandbox of stuff where you can aimlessly wander in any direction and do anything and there's no real sense of adventure, challenge, or surprise as the design is too banal and predictable.
On the other hand The Witcher 3's world is apparently designed differently. The absence of scaling means content within the world is designed in such a way that it exists in a unique state. Instead of wandering over random hills, through random forests, and through random caves with no real care for what's going on, these areas will be set with a particular expected player level in challenge. When done right this is a strong method of RPG/open world game design, ironically in the face of TES scaling accessibility, as it helps keep you believably focused and directed through the experience. If that cave is too tough, you know now is not the time to explore it. If that forest is too difficult to explore, you leave it for later. You end up creating a mental checklist of where you can and cannot go due to difficulty, keeping you focused on the important parts of the game relevant at that time, while also exciting and teasing you with cool shit you know you can explore more comfortably later. It's awesome to have that moment of "Okay, I think I'm ready to explore that cave / wander through that forest I discovered five hours ago!".
Ideally this will also tie into the crafting systems in order to obtain the best loot, quests, monster hunting, and more. Free form open world and content scaling is implemented for accessibility reasons, but ironically I feel it dilutes the identity of the world itself. I mean, it even impacts the pacing of crafting. CDPR have said that you'll need to craft the best items, and I figure like TW2 parts of those "best items" can only be acquired through hunting rare, tough monsters. This ties into the lack of scaling; you'll need to work towards being the right strength and level to match said monster, or even get to the area where said monster lurks. If done well, it prevents you from being able to aimlessly, early grind materials early in the game, or cheaply take on a reputedly strong/rare beast when you're a petty low level. It gives you a goal, a sense of progress, which is the opposite of overwhelming and aimless.
Far Cry 3 is a superb example of aimless, dreadfully paced crafting as it does exactly the opposite; allows you to grind an overwhelming majority of upgrades across the board in the very first ~1/3rd of the first of two maps. Unique animals can be faced (and scripted in area/execution) for their crafting drop irrespective of how far you are into the game, what weapons you have, character upgrades, etc. And pose no challenge regardless.
I really feel one of the biggest flaws of modern sandbox games is how they've embraced the unrestricted openness pioneered by Grand Theft Auto while at the same time try to integrate classical role playing elements like level progression, skills, unlocks, loot, and crafting. The two don't match up at all, hence why old RPGs where those elements are rooted are not free form open world sandboxes to do anything at any time.
So yeah. I think "overwhelming" comes from aimlessness of the design itself, where you can literally go anywhere, craft everything, find anything, fight everyone right off the bat with not a lot within the design to give you purpose, development, or structure in your adventure. Even with a massive open world where you can in theory do just the above, proper difficulty balance and a sense of goal setting and progress changes overwhelming aimlessness into true adventuring and role playing.