@Elithal To expand on what I was saying about open worlds a little, there are three kinds of open world in my eyes.

There is the 'Ubisoft' kind where the open area is trashed with unnecessary markers with the sole purpose of padding out the game to have a longer playtime than it needs, with no markers feeling rewarding or anyhow memorable.. Unfortunately even a game like Witcher 3 borrows from this open world design formula which makes the game suffer if you choose to explore it's world. A real shame for Witcher 3, because despite its combat system, leveling and open world design it's a pretty great game.

Then there is the JRPG type - pretty self explanatory, with random encounters, limited quests scattered around and Pokemon has always fit in this category. Needless to say these large open spaces filled with a bunch of mobs can seem artificial and perhaps to some - boring, but that isn't what people play the games for in the first place. Scattering these same Ubisoft objective markers around the map would detract from the experience of the written story and running into random Pokemon. As a reference back to the Witcher 3, that game would have benefited from this approach, as the game wouldn't seem as unnecessarily busy just for the sake of padding.

The third type is of course Sandbox, these games can vary from Terraria, Breath of the Wild, GTA and give you much more freedom and tools to play with. The games can focus much less on story because they have many features making the open world a more interesting "playground" to explore - hence the name sandbox. Sandbox is arguably the better approach to open world as its focus primarily consists of making a great space with players in mind and attention to detail.

It would be unfair expecting this type of sandbox environment in a game with such a different focus like Pokemon, there is very little conceivable ways as of now as to how it could even be possible without messing with the games' core concept and design.

With that I'd like to add that it doesn't mean that the Pokemon world has to lack in detail. I'm curious to see just how much detail GameFreak is willing to add with the additional power of the Switch to the environments to make them interesting. Running on a screen for 30 seconds with just green grass surrounding you would indeed be quite boring, and it would be nice if GameFreak acknowledged that and added extra flair to the environment for those who are willing to look and find it - time can only tell.