I agree....while Dean didn't have to become Michael there should have been some evidence that it mattered that Dean gave the angels the middle finger. Some sign that yeah......it mattered that they didn't get the "right" vessel.
It would have been great that instead of profession Michael's surefire win in Adam's convenient body that without his true vessel yet fighting Lucifer in his
true vessel, Michael might very well lose. Or that even if he won still most of the planet would be destroyed.
Of course, that lame scene in that field didn't convince that even an ant would die, let alone "half the planet". Pfft. And that is not a budget question as I have seen shows with even smaller budgets pull "end of the world looming" more convincingly than that.
Also, yes, it would have been great had Michael asked Dean one last time instead of going "eh, who are you again? go away."
It made the entire storyline of the angels bringing Dean back from hell and trying to convince him in Season 5 ludicrous in hindsight. If it never really mattered, they could have used Adam at any point. So why didn't they? Plot hole of epic degrees.
The amulet being the object to bring Sam back instead of the soldier on the other hand wouldn't have done much for me. It still gives Dean not even that stupid yellow crayong moment - that goes to an inanimate object - but even if, the yellow crayon moment itself was never good enough for me. On Buffy, I felt that it highlighted Xander's uselessness that he inexplicably succeeded with a cheesy speech because there was no other better way he could have succeeded.
I would have vastly prefered had Dean been the only one to work the stupid rings or anything. In that vein, I would have vastly prefered not to hear from Death himself how Sam is "the only one who can do it" and would Dean please kindly step aside.
I don't buy into this "he has to sacrifice Sam" notion since that is not in Dean's power to do. Sam could have said "yes" regardless and Dean could have lain on the ground inactively while Sam did it all himself regardless as well. So, don't try to sell me glass for diamonds, show.
For the mytharc established for Dean in Season 4 to mean something, I would have required something active and unique to Dean - and I don't mean "he is the closest little moon orbiting the Sam-sun". I mean something tied to Dean himself.
Maybe Zach could have accidentally tranferred some of his dying grace to Dean, giving Dean some boost to fight Lucifer or better say, the moment of surprise to fight Lucifer. Then, while Dean managed to weaken him for a critical second on the outside, Sam used this to gain control for that second on the inside. The cage already open so it's not the ludicrous "overtaking Lucifer for 5 minutes because hey, it's so easy".
Or preferably, yes, I would have gone for BOTH vesseling up and BOTH overcoming their archangels and jump. Why would Dean not make it? Is there any reason to have less faith in him to overcome an archangel than in Sam? It's silly for either, really.