Abrams's style of movie-making is unbearably light and facile, to the point where blowing up multiple planets doesn't even register emotionally - and how did that particular scene even make sense? does this whole movie take place in a single solar system or something?

The Starkiller Base is described as a hyperspace weapon, while the target locations were (supposedly) all in one location, and Expanded Universe physics allow bleedoff of energy or physical interaction between objects moving within hyperspace and normal space (though never for anything interesting to my knowledge). This is kinda goofy, but you're in a Star Wars setting so it's not unreasonably so.

On the other hand, the use of planets to pull the projectiles out of hyperspace doesn't really make sense with how the Falcon breaks through the base's shields, so they don't do a terribly good job of staying with or explaining those rules in the film, and it's horrible at actually passing the impact of what is supposed to be billions of people dying.

I wasn't too put off by the protagonist's Mary Suedom, since she's Corran-Horn level at worst, but agreed with most of the other complaints and frustrations. It's also worth pointing out how extremely unsurprising the film is; even with the vast lows of the Expanded Universe, it picked not from its best moments and ideas but from many of its most unremarkable and boring.