there's been a few interviews where cena talked about how gunn specifically told him NOT to read any of the peacemaker comics because he didn't want that to influence his performance or get caught up in gunn's changes saying, "wait, but in the comics..."
this is fundamentally the issue with DC live action vs the MCU (at least the first few phases anyway). the people at marvel actually take to heart how the characters behave in the comics. while they might not do a carbon copy of comic book storylines and characters, they at least demonstrate a huge amount of respect to the source material. whereas DC just doesn't seem to get that. they know that batman, superman, etc are household names and that they will sell tickets so they write their own power fantasy fanfic and insert popular characters just so people will see it.
then you have gunn... who does the same thing, more or less, but does it with characters that NOBODY knows or cares about. he did it with peacemaker, he did it with suicide squad, he did it with guardians of the galaxy. no one is really comparing these guys to the source material because why would you? i don't know if that's genius or what, but it works