Aziraphale as a natural collectivist and Crowley as a natural individualist raise their beautiful heads once again!
Aziraphale's huge mistake during the Final Fifteen is, obviously, as we've rehashed a lot, assuming Crowley would accept being reappointed as an angel. This isn't out of a lack of love for Crowley as a demon. It's because Aziraphale's first instinct when he's anxious is to look toward validation from a collective of some sort...and the Metatron has just reminded him of what Heaven could "offer" as that collective. A way to do good! Safety! Openness! He doesn't consider how Crowley will feel about this in large part because thinking individualistically doesn't come naturally to him; he's so busy thinking about the joy of Belonging that he doesn't consider how much Crowley values being outside the system - indeed, that it's an essential part of him.
Crowley's mistake, I think, is arguing that it can be very literally "just the two of us." Of course they can be a couple! Aziraphale wants that. He's happy with Crowley as his most unique, enduring, intimate connection. But just as Crowley's individuality is essential to him, Aziraphale is always going to need some cause to serve, somewhere to belong. That's who he is. And he loves Crowley so much that he wants, with utter desperation, for the two of them to belong in the same place, with the same people.
As I've said before, Aziraphale's sense of individuality is growing. He wants to be an individual, not just a faceless, passionless drone in a group of other drones. I think ultimately the reason he loves Crowley so much is that's the gift Crowley's given him - the safety to explore that thing he wants so badly. He needs, I hope, to reframe himself as "belonging" to Earth, rather than to Heaven.
And Crowley does not actually want to be isolated, adrift in the universe with just one other person. He wants to put down roots. He wants to belong somewhere. I think if you had to choose a reason why he loves Aziraphale, that would be it: Crowley can feel belonging with Aziraphale, and Aziraphale also gives him opportunities to connect with others - with humans, specifically - in ways that would ordinarily never be permitted for an agent of Hell. However, he's afraid to make his connection to Earth's community irrevocable, and his fear has always been entirely reasonable, both because it puts his and Aziraphale's safety at risk and because it's heartbreaking to watch what humans do to themselves and each other ("Humans. You don't let yourself get too attached."). He'll have to overcome those fears not because they're so wrong, but just because they're in the way of what he wants.
This is SUCH a good explanation of the central conflict between them. It lays out why they're both going to have to change if they want to find happiness, but also why this isn't an irreconcilable difference. Ultimately, they both love and respect the core of who each other is, and they both want the same things. They're just hashing out the details and working through their flawed beliefs about the world.
Aziraphale believes that auditioning for approval is the same thing as authentically belonging, and he has a whole lot of other flawed beliefs wrapped up in that one that broadly come down to not fully trusting himself on matters of morality and identity. Heaven has exploited his natural tendency towards collectivism for their own ends. That's why I agree that he's ultimately going to reframe himself as belonging to the Earth. That's a conclusion to his arc that resolves the flawed belief while still meeting the need of belonging underneath it.
Crowley believes that by insulating himself from others, he can keep himself safe. Just like Aziraphale's collectivist tendencies are normal and healthy on their own but have been warped into something that hurts him, this is Crowley's natural individualist tendencies becoming maladaptive in response to trauma. He's spent thousands of years forced to hide his care and compassion for others. He trusts a single other being in all of creation and that connection almost gets both of them executed as traitors. Of course he's afraid of letting other people in. The painful truth is that Crowley is not safe. But his belief is nonetheless flawed, because keeping others at arm's length was never really going to protect him. And again, I agree, he's going to have to let go of his fears and commit to his connection with the Earth. I am so convinced that real safety is going to come from letting himself trust and rely on other people, especially humans.
This sets up such an elegant mirrored narrative between Crowley and Aziraphale. Crowley relies too heavily on himself and is unable to trust others. Aziraphale relies too heavily on others and is unable to trust himself. And in a gorgeous piece of synergy, these opposite problems have the exact same solution: they both need Earth. Earth, with all it's fascinating contradictions, is the place where they can at once find independence and belonging; at once protect themselves and challenge themselves to grow. If they can work through the things holding them back, it's where they can be safe and together, existing on their own terms as the versions of themselves they most want to be. Earth is the home they've been fighting for since the very beginning, and all that's left is for them to let themselves have it.