People will tell you not to worry too much about the dissertation. Just get it done. It doesn't have to be perfect.
This is the typical "compete down" kind of advice ("Profacero" 2012).
Allow me to be a bit contrarian here. If you envision a career in college teaching, and view the dissertation and the degree merely as a stepping stone to get there, you can stop reading this post. I am not even talking to you. If, on the other hand, you want to be a serious type-A researcher, then keep reading.
In the first place, the dissertation might be your first book. Do you want to write a good first book? Then pay attention to the quality of the dissertation. Don't write something that you will have to scrap the second the ink dries. You don't want to have to start a second project when you begin your first job. So, yes, people will read your dissertation, if it is your first book. You are 26, or 31, or somewhere around there, when you are working on the dissertation. At what point do you want to be a scholar in your field? It is true that you will be a more mature, and better, scholar at 40 or 50. But one reason is because you weren't fucking around when you were younger.
Be ambitious. Not in terms of the sheer quantity of what you are presenting, but have an intellectually ambitious and challenging project. It doesn't have to range over several centuries, but it shouldn't be intellectually unserious.
This does not mean take 10 years to write it. The tricky thing is you still have to be fast. You have to be perfectionist, at least about the things that really matter.
Not everyone is going to be the alpha researcher. If that's what you are, however, you cannot not be that, except at a considerable psychic cost. If that's who you are, I think you have to embrace it. The competition at the top is quite a bit easy, because you are no longer competing with unserious people. You do need to put in the extra work at the beginning to be serious.