In the end, it is just another Abrams movie: slick, SFX-heavy, and as substantial & satisfying as movie theater popcorn.

Yep.

You might want to add a spoiler note at the top, though.

and how did that particular scene even make sense? does this whole movie take place in a single solar system or something?

Star Wars, as a fantasy film, makes the most sense when planets are viewed as metaphors for cities.

the antagonist is risible

I actually liked Kylo Ren, as what a Dark Force User would look like if one takes the Light / Dark sides as presented. It also neatly matches the story of a child gone wrong instead of a parent gone wrong.

as barmy as opening a movie with tax disputes

One of the things I found interesting about TFA on a meta-level was how little they tried to set the stage with exposition. Why are the First Order the bad guys? Because they wear black and have Nazi-esque outfits. Why are The Resistance the good guys? Because it's right there in the name, they're resisting (evil, one hopes). And... it works. Yes, it's deeply unsatisfying to me to not be able to tell whether or not I would prefer The First Order or The Republic or The Resistance as my government, but that's mostly secondary to the story, which presumes you're on the side of The Resistance.

Was BB-8 the only original and genuinely good part of the movie? Entirely possible.

This seems right to me if you don't like Kylo Ren.

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.