Having read the storytimes just now:
The retcon really does cheapen the character, especially when you get to his funeral, and you hear all about the great things Sentry did, that we never saw, and continuity that he couldn't possibly have been a part of. Later, some authors seem to play with the idea that his presence warps timelines around him in-canon, but this is never confirmed, and it's only used in part of a story told by one character to another character, that is partly used to hypothesize ideas about Sentry. I don't really have much problem with Sentry being a positive force for the people in his life, and this coming from a former mentally ill junkie, because Sentry represents all his desire to do good and be a hero, and Void seems to represent all his hate and resentment. I think maybe the biggest mistake with the character was that in order to make him reusable, they had everybody get their memories of him back.
The original minieseries felt weird, and it felt like it was supposed to, because there's this creeping sense of dread surrounding what's happening, and though Robert is desperate for people to know who he is, this journey comes concurrently with destruction popping up around the globe by the Void, so something feels wrong, and it pays off with the reveal. It ends with everything going mostly back to normal in the MU, and we now know he's a part of it, but in the background. Having to restore people's relationships with him by bringing him back leads to a lot of attempts at pathos that don't quite land, because none of it seems real.