They really do not need to show anything amazing and to be honest for a trailer probably would be best to keep it in the movie. Being Star Wars alone is enough to get people into the theaters from there the movie will sell if it lives up to the expectations.
Personally I find living in the past limits a movie or story especially since that story arc is done. I rather access this movie from what it’s trying to build today and the future of the franchise then live in the past because no matter how nostalgic people are about the previous movies, by today’s standards they would be average movies at best.
I grew up watching all the Star Wars movies, played all the games, read all the comic books and novels. When I look at this trailer I see they are trying to kick start the new series like the old. A beginning where someone average finds that they have a destiny far greater than they thought their life would be. It could be good or bad, but at least it looks like it probably will be entertaining. The trailer is only giving people enough information to let them know the characters from the original is in this new movie. I believe it would be a waste to add anything more that should be discovered within the movie instead of spoiling it early.