The Witness might seem visually appealing on the cover from a few choice shots but once you are in the game it's gaudy in its presentation with its flat colours and minimalist approach. There is also little to no cohesion between environments and the bright colours used, which can be a bit of an eye sore, are worse than Fortnite's making it very kitsch. Fortnite is a little colourful too but by design. However Fortnite blends its environments much more seamlessly and the environmental models may not be as detailed as The Witness's but they do fit the settings much better with slow elapsing of forest say into lagoon or open fields. In Fortnite as a an open world multiplayer game performance is key and here is where it can feel very low poly in its presentation so to does The Witness but not to the extent Fortnite does. The Witness vs Fortnite essentially comes down to gaudy vs moreish. Neither ones design was built to be first and foremost an environment to explore freely and as such admire and contemplate their beauty. Although this is not to say they didn't try. With Fortnite it's more built around a multiplayer experience although a staggering amount of effort has been made to make the world pleasant to be in. And with The Witness although it didn't lack the environmental expertise with it's beautiful biomes and interesting areas, it did however, in trying to make them cohesive, lack the time and budget to make a larger more fleshed out world.
Proteus with one fell swoop beats them both because it is primarily an environment to be experienced first and foremost but also it uses much more lower budget techniques to have a better focused development to priorities on a much more living breathing beautiful world. There is also so much more mystery and evoked curiosity to Proteuses which adds yet another layer of beauty to it's landscapes which the other two games mentioned we're not able to do given there design ethoses. One being a battle royale and the other a fairly straightforward puzzle game: you know what you're in for, Proteus not so much.