I think the writing's mostly fine. The problem is a lack of emotional heft and a person to say "erm, that doesn't work". In RTD's run, he had the emotional bit sorted, but went for crazy epics and a bit of his own "erm, that doesn't work". What both of these things showcases—and this isn't a Who thing, but a modern TV thing—is that there's no script editor with some power working on the show.