Its a shame, but I suspect that its an admission that it will never be competitive and will not help their image and hence sell cars or as they put it "would not be able to reach its ambitions".
Whilst there were some good ideas there, one being not to make an Audi copy, Nissan/Nismo should have realised, at the drawing board stage, that Bowlby's ideas were a bit too strange.
They'll be back, when they can find something quicker. They ought to go 50/50 with Renault, but they're wasting their money on F1 again