I want to comment so much on the fact that, Aziraphale isn't naive for wanting to change heaven, being naive implies that he is ignorant and does not aknowledge that heaven isnt totally good, the thing is, HE KNOWS PERFECTLY that heaven is not good, thats why he being the Supreme Archangel with Crowley at his side was so perfect for him, in his head he was not abandoning Crowley, he could change heaven ways, while with Crowley at his side, and they wouldn't have to care about heaven and hell again, it was exactly what he wanted, it was completely perfect and he doesn't understand why it isn't for Crowley.
Honestly i can't see why people are angry at him, bc it is a smart decision, he wanted to do good from the very start but couldn't do the way he wanted because of heaven, he wants to change things for better. Aziraphale isn't dumb for it, atleast i dont see it, maybe a little confused and with conflited feelings? Of course, but i dont see it being a naive decision.