Season 15 "Carry On” was not as powerful as “Swan Song” Season 5.
In seasons 1- 5 Dean’s fundamental driving foundation is “protect Sam.”
Dean is family oriented and loyal.
He has always wanted a family, whether it was with Sam & John, Sam & Bobby or Lisa & Ben. In his djinn world, his mom, Jessica, Sam and his “girlfriend” Carmen are there. He prioritizes spending time with them and is excited to have dinner together.
His flaws are low self esteem, self-sacrificial, bossy, controlling, inability to let go and lacking in empathy to understand different perspectives. His inability to save people drives him to despair, rage and prone to suicidal behavior. In seasons 1-5 he rarely acts in anger unless a loved one is threatened or hurt.
Sam in contrast to Dean is ideal oriented, academic and self determinate.
He aspires to be a lawyer and live a “safe” “normal” life.
His flaws are arrogance, anger, revenge and prioritizing himself over family.
His failure to prioritize Jessica and warn her about his visions leads to her death. Sam running away to Flagstaff and off to Stanford has harmful consequences to his brother Dean. To the point where Dean wasn’t sure what he was going to do if Sam told him to leave in the Pilot episode. Implying Dean was unstable possibly suicidal. Worse he thought Sam didn’t care about him.
The ending of Swan is perfect because it deals with their fundamental character flaws. Dean’s flaws drive Sam’s flaws.
Dean has to let go of Sam to save the world. He has to learn to view Sam as the adult he is because if he does that he can let Sam make his own choices. Part of Sam’s flaws result from Dean not giving him freedom of choice. Sam therefore acts on his own whether by leaving Dean, drinking demon blood or not mentioning his visions.
By letting go of Sam, by letting go of his control, Dean is learning to live without Sam. He is learning to become a more selfish person and how to be independent. He is rewarded with Sam’s blessing to go form a family with Lisa and Ben. He still has self-esteem issues but learns to live without Sam. Given time without Sam coming back I think he would of gone down the route of Sam’s family storyline in “Carry On.”
Sam’s character flaws lead him down a dark path and almost cost him Dean and Bobby and results in the breaking of the final seal. Sam amends his actions by learning to control his addiction, learning to work with Dean and controlling his anger.
Dean finally getting the family he always wanted and retiring from a life of hunting in which he was “barely holding it together” is a reward for his sacrifices over the years.
Sam grows as a person by moving past himself and finally gains the recognition from Dean that he always wanted. While not a happy ending for Sam it is one where he grew into his ending.
The issue with the way “Carry On” ends is that at this point neither Dean nor Sam believe they can have traditional families and live normal lives. Both have tried and failed multiple times with friendships and romances.
Dean had to give up Lisa and Ben to keep them safe. He’s watched Castiel, Jack and Sam die multiple times. We learned that on top of giving up his love interest Cassie(S1), he had to give up his childhood romance Robin(S8). He killed his friend Benny to save Sam. As long as Sam is alive Dean will always chose Sam.
Sam has a similar experience to Dean. Losing both Jessica and Madison. He also chooses Dean over Amelia much like Dean chose Sam over Lisa. Dean asks Sam if he would ever consider settling down with a hunter. Sam says he hasn’t really thought about it. It also would be hard to consider for him as he loses Eileen. In Season 9 Sam tells Charlie that he used to think that he would go back to his old life, to law school. However he has accepted this is his life now. He doesn’t want to do it without Dean.
When John Winchester is disappointed that both are still hunting and without traditional families Dean expresses that he’s happy with their found family. I think both Winchesters also recognize their family is always in flux due the nature of being a hunter.
At this point in the story Sam and Dean have repeatedly chosen each other over others. When Jack seems to be in control of his powers they both contemplate going straight to retirement. They only express going out with a bang whenever a big bad is put in front of them.
That’s what makes Sam’s end storyline confusing at this point he pretty much settled on die hunting or retire with Dean. He has never expressed wanting kids or a wife in the way that Dean has. Sam mostly wanted safety and to put down roots. If they wanted to set Sam up for this storyline they should of given Jack a more central role in Sam’s story. Where Sam would be set up to be more fatherly towards Jack and expressing hopes to have kids one day. Rather than him having a few meaningful conversations with Jack. Give them more bonding time. Or he could of built a relationship with Eileen in which creating a family could of been mentioned. It was quite out of the blue. Particularly since he appeared to have given up on those dreams with Amelia in season 7 and dedicated himself to hunting. Rather I would picture Sam without Dean as an academic being more likely to rebuild the Men of Letters to carry on the Winchester’s legacy. Or leading and organizing Hunters like Bobby did prior.
If Dean lost Sam and was told to keep fighting I think he would be the one to create a family. Dean always wanted a family and has demonstrated an ability to be great with kids. Dean only believed his fate to die young because it’s what he saw happening to other hunters. His wish to go down swinging was always tied to how hopeless he felt. This sentiment was strongest when he still had the Mark of Cain. His anger and drive to hunt were driven by the need to protect people from ending up with the same fate as his family. Also being put through Chuck’s multiple storylines he lost hope of ever finding a normal as a new big bad always appeared.
At the end his adoption of a dog into the bunker and a messy room show him enjoying his life. He’s not acting like a desperate unhappy man anymore. He was willing to sacrifice Jack so him and Sam would be free. Dean is typically the first one to jump at the self-sacrifice so letting Jack sacrifice himself is a big indicator of how much Dean wanted to be free. Him dying early was not a fitting end. Even worse they revert his character progress by saying to Sam you’re stronger than me and indicating he wouldn’t know how to live without Sam if the roles were reversed. Even when he does figure out how to live without Sam at the end of season 5 or in purgatory with Cas.
In either case the implication of him dying on a rod is sad. It implies that without Chuck’s protection the Winchesters are not as good of hunters as we thought they were.
The ending itself is not bad, but I wish their approach to it had been built up over the season rather than a setup in the final episode. As it stood Dean and Sam had both been resolved to not ever being able to achieve normal.
Sam didn't have a deep yearning for a family that was finally filled. He no longer felt a pull to a normal life. His character flaws from Season 5 were resolved and few new ones were introduced or were long lasting. Sam was already his best self.
Dean died with self-esteem issues, an inability to live without Sam. His anger issues were introduced season 9 yet never resolved. The closet we come is to Dean saying he's not a killer to Chuck. If anything this episode regressed his character by giving him the death Mark of Cain Dean or Michael!Dean would of wanted. Not the one a Dean 15 would of wanted.