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If there's one thing I really appreciate about the DLC it's the lack of padding.
In old pokemon games routes often relied on trainer battles to pad them out, because without them many would take seconds to get through (Pic related). In the dlc, there are no trainer battles, the focus is on exploration, and as such the areas end up feeling designed around this.
They're laid out like big open areas with many items scattered throughout, populated only by wild pokemon. It puts the focus on the exploration, and so you get nothing but exploration, without much interruption.
Routes are designed more so to funnel you into trainer battles, often the only actual choice is when you choose to get down a set path to find an item, or choosing between 2 separate paths often with their own pros and cons.
I'm not an idiot who thinks it's all hallways though, the route designs were clearly meticulously thought out in their own way, and are well designed, but the much more open nature of the IoA and CT are just a better fit for pokemon and make the exploration feel more real, like you're actually exploring a place instead of progressing along a set path
Gamefreak stumbled upon an actual good direction for the series, I seriously hope they realize this and embrace it, gen 9 may actually be good