I do find this opprobrium towards Ray Stenning and Best Impressions perverse to say the least, particularly when he's getting the blame for a scheme that he's not responsible for.

And who'd have thought so many graphic designers would be on this board
The reality is that most design agencies have a house style. Should an operator want something completely new, then I'm sure that BI would do it. However, that they can reuse designs and collateral means that they can create a livery plus all the other marketing collateral at a lower cost.
Also, liveries that are designed that reflect the two main manufacturers styling so they're going to look similar. I might also add that this is of little interest to the 99.99% of passengers; if you're a passenger on the Norwich Park and Ride, are you going to know that it's similar to Buses of Somerset? I'm guessing not.
Opinions are personal but I do tend to agree with the overall view on the GNW livery; it's restrained bordering on dull and I was thinking they might have gone for something bolder and brighter as a greater break from the past.