I think u missed the point of Cirrus’ development. If what you wished had become real that would have been there was no development.
Skylar was a key part of Cirrus' decision to stay, not only because of his unconditional support, but because Skylar knows first hand that “running away” to another place doesn’t automatically mean tha you will get better. Change starts from within, no matter where you are.
Cirrus is trying to run away looking for “salvation” and this won’t help him at all in the long run. Because what he’s actually looking forward is right there in Seoul.
Skylar, having learned this lesson on his own way, gives that “little push” to Cirrus that he needs to see and that there is not need to go away to find peace or courage.
Thanks to Skylar, Cirrus stopped bearing the inevitable guilt and learned to open himself to the idea of actually having people who love him and support him.
The decision of staying not only allowed him to stay physically, but even emotionally, by accepting that he has a place and person who believes in him, an opportunity to grow, explore and heal without running away.
THAT is Cirrus’ development.
From the start I wanted them to end up together but now that it's actually happening, I'm lowkey disappointed. I can't help feeling sour about it, after everything cirrus went through and everything that happened, I wanted him to finally be free from all of this and leave this life behind, find happiness somewhere else and someone new but ig that's too much to ask for :/