From what I understand, that's kind of the point of a watercolour aesthetic.
Anyways - if you move close to a watercolour painting, you do not begin to see the big square pixels, right? So if the textures were of higher resolution they could stil preserve the watercolour quality, but they woudl be not as pixellated.
Take a look at these screens - are they consistent with "watercolour easthetisc", or simply blurry?
http://www.imagebam.com/image/3bbe3f214314662
http://www.imagebam.com/image/c7d0ac214314772
http://www.imagebam.com/image/6e5fa0214314731
Finally - does watercolour aesthetic prevents gamers from being able to read this leaflet? http://www.imagebam.com/image/4e0667214314736