Originally posted by Bandy:

Now have to ask, if the game runs well with better textures, why the hell would devs have been happy with pixelated grass and leaves? It makes no sense.

The low-res style is the aesthetic of the game that the developers did on purpose. In any case, there are oodles of mods to change all sorts of elements of the game. If a nuftie like me can figure it out, so can everyone else. :) Have fun!