I think the biggest problem Episode 7 had was that they tried to make the villain the protagonist. Or at least he's the closest thing to a protagonist we got among the new characters. And his story is weak currently because they painted him as someone who wants to be evil for the sake of being evil. So his motivation isn't at all relatable. And yeah without a relatable protagonist, you don't have a very compelling story. Much better storyline for the whole new trilogy might be something along the lines of the new generation having lived in a galaxy with no central order (after the defeat of the empire and death of the emperor and darth vader) long for the days they here stories about when the galaxy was united (both under the old republic and the empire) and long to bring that unity back. Then have characters like Kylo find themselves justifying horrible things and slipping every closer to the dark side in an end justifies the means kind of mentality. That could be a good story setup, the new story as it stands now doesn't really feel set up, just feels like a remix of "essential star wars plot points".
Yea, the cool thing about the original movie plot is that darth was like hitler trying to take over the galaxy with his very well equipped stormtrooper army and they didnt portray him as some mad, unstable dictator but rather as a very calm, calculating and poised leader. The rebels also had to come up with an ingenious plan to attack a virtually impenetrable fortress... but I think it was the personalities of the characters that really made the movie. Even Darth's menacing presence and evil sounding deep breathing added to the charm of the movie..
[video=youtube;y1zzzRXwP64]https://www.youtube.com/watch?v=y1zzzRXwP64[/video]