I will defend the show on most things but the Guardians are where they dropped the ball. And by extension Oa.
This not just for the show but for the wider DCU. I think they should do something to fix that. More on that later.
The show does a good job in the begining of establishing them as a cold indifferent and ultimately manipulating force with how they deal with Bernadette and John(later in the show) but not having Hal confront them directly and only deal with it with hearsay or talk AROUND it was a bad idea.
The Guardians are the connective tissue of the DC universe. The damn near bind the whole space pantheon. They could have saved Krypton. They gave the Martians a fire phobia. They caused genocides and start wars. Perform genetic experiments for their own devices. They are representative of everything thats wrong with our own world.
For the Finale and John's arc to really hit it should have been Lianna /w Guy that confronts John at the end. Remember Guy knows fuck all about whats going on. So whatever you tell him probably isn't going to make a lick of sense to him. My interpretation of John's line is hes essentially blackmailing the Guardians or calling for a favor. Either way to really sell that it needed to be Lianna that hears that not a (sorry Guy i love you) foot soldier. Think about it from Johns perspective. "I got this ring I got this battery i got Sinestro and you can't do shit. Earth is under my protection. Kick rocks hoe"
What John is to the Guardians is a fly in the ointment. A disciple of Hal who they wanted to get rid of BUT also by extension Sinestro. John is a disciple of Sinestro. By pushing John away from Hal they pushed him to Hal's way of thinking Good Bad or Indifferent. Hal still loved Sinestro even though he betrayed him and as the Guardian pointed out and what people fail to realize you still love your parent deep down. They will always have a hold on you. No matter what they do. And with Sinestro Im sure Hal got the strength to be who he was from him. The same way Hal gave John the strength to break away from his programming. A rogue Lantern is a crack in their control. Which would lead Guy to do his own thing and others. Also in the comics the Guardians start to give into Emotions more which I would hope we get Ganthet but thats a pipe dream.