I do get what you're saying and agree with you up to a point, but I think it's possible to create the feeling of reality and adventure whilst not being too serious and bringing in brighter (but tasteful) colours and elelments of humour. I know I keep going on about colour but Wild Asia looks dire if you askk me. Just dull, drab and grey with only a few bits of bunting to add anything to it. Compare this to Asia at Disney's Animal Kingdom, which is actually my favourite themed area in the world, and the lack of 'anything' in Wild Asia really becomes apparent.
This, I think, is the problem. If Chessington have looked at the elaborate and, quite frankly, spectacular theming of Animal Kingdom's Asia and hoped to re-create it at Chesington, this was a very unwise move as they really don't have a Disney budget, so what we are left with is a dull and uninspiring area.
I get the idea that Chessington's new approach is creating reality and less 'wackiness' than in the paast, but even the realistically themed areas which you list, such as Mystic East and Forbidden Kingdom, still have varied and more vibrant colour schemes as well as elements of subtle humour making them nice places to stay and spend time. After 5 minutes in Wild Asia, I'm ready to leave and Zufari does very little to get me excited or justify a re-ride. I really just don't think Chessington are getting it right in how they're theming new areas. Good intentions may be there but, certainly in the case of Wild Asia, they just aren't properly followed through meaning that the finished product is, for me anyway, something of a disappointment.