As monumental as the confession scene was, it kinda leaves a bad taste in my mouth that Cas only confessed because he was going to sacrifice himself. Like, Dean's worthy of being saved, but he's not worthy of being loved in a way that's not going to wreck him long term?
Well, I think we can safely say Cas did not mean it this way and would be horrified if confronted by this angle, but that it would be well within Dean's perspective (built on his own experience) to think of it that way and become even more convinced that loving him is a death sentence and that everyone will always leave him. Multiple people have proved they're willing to die for Dean Winchester and there's nothing special about it (from his perspective). He wants some to live for him instead.
Cas doesn't really know how fiercely Dean mourns him when he's gone, and while I think he's cognizant of Dean's insecurities to some extent, I'm not sure he realizes exactly how deep they go. Even if Cas was told like "Well when you were dead, Dean spent months drinking himself into the ground" or "When you and Mary and Crowley were dead, Dean had a suicide kit and he used it and when you came back he said it was his 'big win'". I sometimes think Cas would have trouble processing that he'd have anything to do with Dean's bouts of depression because of his own hang ups.
See: Cas hearing Dean pray to Cas every night for a year, searching for him through Purgatory, and Cas never getting it through his head that whole time that Dean wasn't going to leave without him and wasn't interested in his self-flagellating isolation play to "protect" Dean (which—if we're being real—wasn't just about protecting Dean).
See: Cas hearing Dean stress throughout season 12 that he worries about Cas when he goes radio silent on them and that he wants them to communicate with each other and work as a team, and Cas going "okay" then stealing The Colt so he can go radio silent on them and get a win all by himself and decidedly not as a team because Cas does not want that.
Like. There is clearly a HUGE disconnect between them when it comes to how to communicate as a team and what it means to protect the people you love. More than that—their own psychological needs and desires for themselves as individuals seem to vary quite substantially (and they clash and create more miscommunication). They both crave safety and stability, but to Cas, safety and stability means knowing "I got a win, I did a good job, and now when I go home I feel respected and needed" and to Dean, "a win" means his family is safe. To Dean, safety and stability means, "We are all together in our home, and we tell each other where we're going when we leave. We handle things as a team and communicate with each other instead of going behind each others backs."
Cas really slots himself into the protector role and I think to an extent, Dean is willing to concede that role to him. See: Rocky's bar, where Dean imagines himself as retired and working as a barkeep. He's still perfectly capable of defending himself, but he doesn't go out looking for hunts. Sam and Cas are still hunting, but Dean feels psychologically safe about it because he knows where they are, and they always come home to his bar to see him and to be fed. In real life, Cas slots himself pretty aggressively into the protector role, but he doesn't communicate and doesn't always value teamwork. He doesn't realize while trying to "protect" their family that his aggressive tendency to isolate from them to "protect" them is 1) reminiscent of Dean's father and 2) distressing to Dean because Dean doesn't know (as a person who has lost many people he cares about including Cas multiple times) where Cas is or that he is safe or if he needs their help. Cas also doesn't see his tendency to lone wolf as abandonment and doesn't see any self-centeredness in it, but Dean does (and I don't think Dean is totally off—just like I don't think Cas was avoiding Dean in Purgatory just to keep Dean safe and for no other reason).
Anyway. All of this to say. I have said in the past that it is very possible that Cas would avoid Dean if he came back after The Empty took him. But say Cas did openly and with abandon continue to acknowledge that he loves Dean. I think if Dean withdrew from him, it would be so much fun if it was less out of timidness and fear and more out of anger. Dean knows what Cas is trying to say, but Dean doesn't feel understood, and he doesn't feel loved even if Cas loves him, and I could totally see a reality where Dean tries to give Cas a taste of his own medicine by making Cas chase him all over the country about it in a game of cat and mouse. Obviously, Cas is growing increasingly impatient and angry about this as he pursues his charge and intense sexual tension is building the whole time so when Cas finally catches up to Dean they aggressively fuck each other about it.
