I hear you.
I also have been trying with everything that's in me to find some kind of a silver lining in this mess of an ending, too.
And FWIW, the small one that I came up with is not that different from yours.
For me, Sam losing Dean for years finally gave Sam a better perspective on how much Dean's life truly mattered in Sam's own.
I never felt that Sam really and truly appreciated Dean's presence enough in his life, but being without Dean all those years?-well, hopefully that did the trick.
And yes, Dean in Heaven, and not having to suffer that particular lesson was not only poetic justice, AFAIC.
I would also call it Grace-which Dean so well deserved, IMO, and had earned 10 times over in his short lifetime, again, AFAIC. And this, even though Grace is sometimes deemed by humans to be something that is not always thought of as being deserved or earned, but only God-gifted and given.
And that sort of fits in with the roots of this show, in a way, too.