Saw credits on this a couple of nights ago, The PS5 timer said 13 hours but I think it has to be longer. I was certainly not rushing through it, although it didn't take me many days to finish.
This is a bit "Uncharted in Space". There is exploration, and then there are encounters with bad guys. Sometimes a bit of flying, but those bits are rare.
The highlight here is the story. It's fantastic and kept me coming back until I was all done. The characters are all good, Drax is a highlight and most of his lines are hilarious. The story and characters are a mix of the comic and movie versions. Star-Lord is mostly the movie Star-Lord, though.
The only real problem with the gameplay is the start of the game. You can watch the first couple of hours of this game and it might very well put you off it. The first enemies are bouncing balls, bouncing cubes and spiky things. They all look a bit rough, and you run around them with your underpowered guns and make the other characters do the occasional attack, one for each of them. It's a bit dull, and only the story and environments will keep you going at this point. But after a few more encounters, you update your guns and your team's abilities, and everything becomes a lot better. Rather than being a bit of a chore, the encounters become exciting tactical battles. Near the end, I was never annoyed to go into an encounter with enemies, but excited. And the late boss fights are marvelous as well.
It's not without complaints though. It can be buggy at times, and within the great graphics there are rough spots. One time I saw an early bad ending because a button prompt didn't appear on screen. But it allowed me to start again just before. Finishing moves on enemies can look a bit naff, not nearly as polished as Amazing Spider-Man was on PS4. The gameplay design allows Star-Lord to fall off platforms to what should be his death, only for him to spawn again without any consequence. It's hard to tell just how much the player choice matters, although I know that one of my choices made for a very funny, although foreseeable bit at the end. Also, I'm not sure if it was only my choices or the game story, but Rocket was pretty much insufferable for a quarter of the game. Once he snaps out that bad mood, he is as funny as the rest.
So all in all, I was very impressed with this game and hope they get a chance to make a sequel.