Sure it does, because there's enough backstory baked in to the movie and all of the plot points in Two Towers are mostly self-contained.
Same thing with A New Hope. That's number 4 in a series, and it makes perfect sense.
Also, the first of a trilogy abso-fucking-lutely better make sense without any outside backstory. If it doesn't, the writers have fucking failed.
Here's the thing: A New Hope was the first of the entire series. It was written to be stand alone in the event it wasn't successful, but Lucas had intentions of creating more stories.
When you aren't sure of how far you can take your story, you make sure it is mostly contained so that at least is still feels like a coherent and whole story.
Every other movie in the series would feel flat without the Star Wars history already set up.
Yes, this is the fist movie of a new trilogy. But it is not the first movie in the series. So I think exceptions to that expectation are in order because it's entirely known that more movies are in the pipeline.
Granted, I do agree that they could have invested more time toward backstory, but I can also appreciate how they just started at the middle and will let the backstory fill naturally. It was fully understood more movies will follow, guaranteed, so they have the opportunity to start strong without exposition and let that fill in later.
They had more support for Maz filmed but cut it out from the theatrical release. That was beyond stupid IMHO. I guess a lot of what was cut probably actually made it more interesting, but perhaps they were afraid of pushing a SW movie to the 3 hour length. And I think they wanted to save some reveals for VIII.
So yes, I wholly agree it could have been a better movie, but I feel it is excessive to complain about some things when this is a movie starting a new trilogy that is guaranteed to be filmed (guaranteed, yes) in an existing movie universe 6 chapters deep already.
A lot of movie trilogies, the first movie is actually a little more succinct because they are often testing the waters. If it is based on a book, the book itself was a test, and when it was successful the author was encouraged. Same for movies, when the studios come back with the green light.
So to be fair, we have this expectation baked into our heads, because we have seen this repeated often. But it is not for the goal of story telling that it is like that, rather, because of uncertainty. When it is an absolute certainty that Episodes VIII and IX will be filmed, I think you are afforded to luxury to actually officially launch that trilogy with full intent to keep some things unexplained for future scenes. Think of it as not 3 movies but as one big story. Any good story does not start off heavy with exposition, the general rule of thumb is for the author to start somewhere near the middle and let the backstory fill in naturally over time. They are at the 1/3 mark of the new story, I think it's fair to give it a chance. So it made the first entry a little weaker as a stand alone film, but I think as part of the greater whole it will be appreciated at the end, and I am excited to see where they take it.