Ok bad is too strong of a word. But I do feel that they might have took a lot of resources and time to create. Therefore, a lot of features that could have been in were probably scrapped.
You generally don't start complaining until after you know wtf you're talking about. How many people did they have to make Oblivion? Maybe 1/3 of what they got today. You really think the creating of dragons is a bad thing? Dude, that's like saying that Bethesda don't know what they're doing. Maybe you're the one who should get yourself a little updated on things.
Adding dragons to the game is like adding any other enemy. The only difference is that todays 3D models usually have a lot more animations than yesterdays models - And, since the dragons are the primary enemy of the game, they necessarily use a little extra tiome on them. It's all about selling the game with the right elaborated features. But that's because it's expected, plus today it's much easier to add content to a game. For instance, the size of Starwars The Old Republic could easily be 2-3 times the size of WoW, because today they got better and faster tools to get things done. That means more time doing programming, extra details and features and more. This is why Daggerfall was 90% generic, because otherwise it would have major limitations compared to games today - and Bethesda has always been about "huge, open-ended worlds".
Not to mention the money. Oblivion is to this date the Best-selling PC RPG in history, and Fallout 3 may yet beat Oblivion over time. I'm not sure, cause I haven't checked the current sales numbers of F3. But in any case, I wouldn't exactly say that Bethesda's got a problem with extra manpower.
Lastly, there's the investment. All features of a game is a major investment for potential game sales. The fact that dragons are in the game and you're able to fight them in a way that has rarely been done before, if at all (WoW and similar games would be the closest to it), could very easily mean a major sales increase if they manage to advertice it properly. If most people aren't that hung up on dragons, the sales would just increase a little bit. But if fighting dragons "the real way" is what most players have always wanted to do, then the sales could go up several hundred percents at most. You never know exactly the outcome.
All I know is that Skyrim is almost guaranteed to sell better than Oblivion, if the game is relatively bugfree (like Oblivion) and without too many "points of aggravation" (i.e. features that annoy the player more than excite him).