Guardians of the Galaxy Vol. 3 beautifully concludes each character's arc.
Guardians of the Galaxy has always been about finding a chosen family, with each movie acting as a different stage of growth. The first movie had a group of practically orphaned individuals come together. Peter Quill (Chris Pratt) was abducted from Earth as a child and raised by intergalactic thieves known as Ravagers. Gamora (Zoe Saldana) was kidnapped and adopted by Thanos after he destroyed her planet. Rocket (Bradley Cooper) was an illegal animal experiment who escaped his captor and befriended Groot (Vin Diesel), a tree-like humanoid. Drax the Destroyer (Dave Bautista) was a warrior dead set on avenging his family's wrongful death.
During Guardians of the Galaxy Vol. 2. Peter learns his father, Ego, is a celestial being who manipulates and murders innocent people from other worlds for personal gain. When Peter's life is at risk, Nebula (Karen Gillan), Gamora's adopted sister who was tortured by their father who replaced her body with mechanical parts, and Mantis (Pom Klementieff), Ego's naive assistant with empathetic powers, join the Guardians to save him.
Being part of the MCU, The Guardians helped the Avengers defeat Thanos, but it meant Gamora dying, and a past version of her who's never met the Guardians survives. The Christmas Special reveals that the Guardians have found a home on Knowhere. Drax and Mantis try to cheer up Peter, who is depressed due to Gamora's "death," by celebrating Christmas, a holiday they don't completely understand.
Throughout their journey together, The Guardians of the Galaxy have undoubtedly grown closer as a family, giving each character the courage to find their true purpose in Guardians of the Galaxy Vol. 3.
Because Peter is still grieving, Nebula takes on more of a leadership role. The other Guardians are still trying to build a life on Knowhere, but we're not introduced to what that looks like. When they're not out saving the galaxy, who are they?
When Adam Warlock (Will Poulter), a gold-skinned supervillain creation, attacks Knowhere and Rocket is left injured, the futuristic med-packs don't work because he has a kill switch around his heart. Instantly the Guardians leap into action to help their friend.
Throughout the film, the characters are forced to face their truths. Drax is stupid, Mantis doesn't understand social cues, Nebula is mean, Peter rejected his family on Earth, Gamora is not Gamora, Rocket is a raccoon, and Groot doesn't say more than three words. They all have to adjust to what these truths mean for them as a group and as individuals.
While facing off against The High Evolutionary (Chukwudi Iwuji), a mad scientist who considers himself god for creating multiple civilizations after various illegal animal experiments such as Rocket, the team falls into their old roles. Peter leads, Nebula begrudgingly follows, Drax and Mantis hilariously fail at doing their one job, and Groot is the muscle. However, they quickly realize things are no longer the same, not just because Gamora and Rocket aren't there, but because they no longer fit into these roles.
Because Peter was so depressed, Nebula learned to lead not follow. Drax and Mantis have had enough time to contemplate what their purpose in life should be. Drax discovers he was always meant to be a father. Mantis doesn't come to a clear conclusion but now dares to venture on her own to discover it. When Peter finally accepts that Gamora has found another family, he returns to Earth to learn about the family he left behind. Rocket comes to terms with his identity as a raccoon. Probably most interesting of all, Groot speaks, and we understand him because, like the stragglers they pick up throughout the film, we have been officially accepted into the Guardians of the Galaxy family.
Guardians of the Galaxy Vol 3 might've ended with most characters going off on individual journeys, but they are not orphaned the way they were when we were first introduced to them. These are fully rounded individuals who, through their found family, have gained the courage and ability to desire more out of life. More importantly, they know if they fail or falter in any way, it's okay because they can always go back to Knowhere, and their family will be there waiting for them.