There was so much to say about this episode but I think the writers summarising it as a “love letter to the fans” couldn’t be more accurate. There were so many hints to the fans being important and almost essential to the shaping of the show and keeping the show alive.
Personally, I thought that the play symbolised how the cast and crew want us to interpret the show however we like because we are the reason the show is still running. Although Dean is initially frustrated at the changes that the girls make to the story he eventually learns, through it being the solution to killing the monster of the episode, that putting our own “vision” or “subtext” on the story is always good and is what makes Supernatural so special.
At the end of the episode Maria gives Dean the samulet prop that they used in the play, stating what every fan agrees with which is that he should have never thrown it away. Jensen Ackles admitted that the amulet that Dean wore from Season 1 through 5 was very heavy and would hit him in the face during fight scenes so it’s obvious that he would never return to wearing one. However, I think that the way Dean put it on the rear view mirror of the car was a much better shout out to the fans.
The samulet symbolises us, the fandom, the fans that are so passionate about the story and all of the messages it brings; love, death, family. Everyone who works on the show are acknowledging us and are saying thank you in their own way. The cast and crew are demonstrating how close they are to us and how much we help Sam and Dean stay strong.
We are now truly there. We’ve made it. We are in that car, with Sam and Dean, riding down that road, fighting the good fight with them.