The unpaid people who make those unofficial patches do a pretty good job. You're saying Bethesda isn't as competent as modders without access to the source code?
No, I'm not. But just a heads up for you, fixing bugs can also introduce new ones to the mix. Even seemingly easy to fix glitches, like the one involving the dragons flying backwards one, can cause numerous other problems that may be much more subtle. As well, the modding community has a significant advantage: It's not their job. Studios have deadlines and budget limits and the like. The more time you put into the little things, the less time and money you have to develop the larger aspects of the game.
So as I said, bugs are going to exist, even after modders have had their way with the game. The only difference will be in the size and severity of the glitches.