SPOILER ALERT!!!
Do not read if you have not yet seen Star Wars: The Force Awakens
I have to disagree with the comment on character development. In this latest movie, Rey does not have an Obi-Wan who can pull her aside to train her in the ways of the force. This looks like this will be changing at the end. And no, they don't have the bickering/adorable equivalent to Hans/Leia in the latest movie, but they do have what is looking like a possible romance building between Rey and Finn...at the least it looks like a solid friendship. As for Finn - he overcame his Storm Trooper "programming," then after escaping, abandoned the Resistance, then overcame his fear to rejoin them when he witnessed Rey's capture.
Then we have Kylo Ren, who is revealed early on to be the estranged son of Hans and Leia. He has chosen the dark side of the force, but is struggling as he is being pulled by the light. He throws temper tantrums when he hears reports of battles that did not go the way he desired or when someone escapes. He also has conversations with Grandaddy Vader's helmet. I'm not going to spoil what he does at the end (though I'm sure everyone reading already knows), but I would argue that he is further developed as a villain than ol' D.V. was at the very first movie. Yes, they developed Vader quite a bit further, but that was in the second and third movies (of the original trilogy - Ep. IV, V, & VI).
So I think they just went with different directions in developing characters than they did with the first movie. I'm glad of this, because other parts of the movie were far from original. I did not like the plot of BB-8 having the secret data that the bad guys need...that is the very same plot of Episode IV. There should have been a better way of bringing the feel of the original ground-breaking movie that Star Wars: A New Hope was without retelling the plot.
You are thinking of rated R, or "restricted" movies, which requires one to be 17 or older unless accompanied by a parent. PG simply means "parental guidance," to indicate that there may be some material that younger audiences may be upset with...such as the fox actually getting the rabbit instead of it getting away, or some-such. You bring up Spielberg, which is interesting, because his Indiana Jones and the Temple of Doom, received a PG rating. The violence and subject material in this movie is far more intense than most PG movies, yet it did not meet the criteria at the time to merit an R rating. Thus they created the now-familiar PG-13 rating, which strongly suggests to parents that they think twice before letting their children watch a movie with that rating.
That's how it works here as well:
G - general audiences
PG - parental guidance - still pretty mild, may contain a swear word, but no F-bombs, still any age can see
PG-13 - probably more violent than PG and/or may contain saucier language, may contain some brief nudity
R - no one under 17 admitted without being accompanied by an adult. This may or may not be enforced by the movie theater. Usually will contain more profanity, more nudity (possibly frontal), violence more graphic than PG-13.
NC-17 - No one under 17 admitted, period. Think of it as one step away from porn, or porn trying to be "artsy."
X - porn
And to confuse matters more, this varies. Drug jokes that would have been okay in a PG movie in the 70's would now have the movie receive an R rating based on today's cultural climate. Conversely, nudity that would merit an R rating in the 70s may receive a PG-13 rating today.