I think that's because they've been told (by governments, government appointed cronies and also by the public) that they're just another broadcaster who needs to compete on the same basis as others. So in some parts of their portfolio they increasingly make the same lowest common denominator shit as other broadcasters. There now seems to be insufficient people (within and without) who care about the spirit of the BBC charter for them to have the guts to live up to it. The public gets what the public want.