It depends on how you play Galactic really.
There's a more control/spread based version and then you have your standard toolbox version that almost everybody uses.
The Toolbox one is good, but it's very much beatable. The hardest thing is playing around Power Sprays. If they use Honchkrow and stock up on Power Sprays, then they can essentially stop you from setting up. BUT, usually they will run out of Sprays and you will be good to try to recover.
The control/spread based one is trickier to beat or tech against. You will be power locked close to every turn, so in order to play against it, you really have to get lucky with your drawing and try to set up as many of your Pokemon as you can. They will aim for your basics abusing the Crobat G+Honchkrow G sniping, and Palkia G can also do its fair share of damage. It's weakness is Looker's Investigation and cutting off their Uxie's or Palkia G Lv. X.
I'm not sure I answered the question, but bottom line is, Galactic decks have the most balanced combination of control and beatdown that we have seen since Plox, so naturally it will be a very attractive deck to play. It has its weaknesses but Power Spray is really kind of a broken trainer that CAN prevent setup completely. I've played a couple games where I Power Spray their Uxie drop and they just can't recover. THAT, I believe is what really makes Galactics good. They are just really good at stopping you from setting up, better than any other deck in this format.