/They seem to have laboured under the assumption all along that certain things in the books just wouldn't work, without even trying them out./
I agree. But when you're on a tight shooting schedule, there are many things you simply never get to try out, let alone conceptualize. I think the sheer enormity of the project essentially doomed them to making certain clumsy moves. When you're in charge of something that huge it's hard to keep all the pieces together.
They gave us three movies in three consecutive years, but that's a tough pace to keep up with. Perhaps if they stretched this out over more time some of the more glaring imperfections would have been smoothed out. But we all live so fast these days.