Honestly i'm not trying to sell the game to you or any other, because imo very few people would be able to go through its faults and see the (many)good things it has, i'm just trying to make people understand that the game is not as bad as they think(without even trying it).
You see mostly the same outdoor environments because:
1)at the beginning most of the unlocked locations are outdoor
2)all the videos show only the first hours of the game(and even reviews clearly didn't bother to go on, some of them don't even know what they are talking about)
The same applies to game features.
New locations unlock after many hours, to see class switch effects you need first to level up a class a bit obtaining some of its abilities and only then to change with another class, and so on, all things that require time.
The only article written by someone who seems to have really played the game was from Kotaku, but the fanservice was the argument, not the game, this is the only bit about the game itself:
http://kotaku.com/why-im-avoiding-one-of-the-main-features-of-valhalla-k-668967062
Locations are mostly 50% outdoor 50% indoor(caves count as indoor right?).
VK3 is not a looker but Vita got worse looking games that graphics-wise were not as destroyed as Vk3, as i have already said VK3 is an easy target for the ignorant hate.