Post-Rebellion stuff always have this depressing feeling. Even if the ending is happy, you can't help, but feel weird.
Considering the most likely interpretation of Rebellion's ending is Homura's interpersonal relationship with Madoka is over, for good I'd call this an optimistic take.
It's interesting because I always considered Rebellion to be the optimistic outcome to Madoka. People always talk about how Rebellion's ending is tragic and dark and that it's your classic bad ending that Urobutcher is known for. The thing is that the world is practically not that different from the original series's outcome. The TV series basically ends with Nobody remembering what happened except Homura while Rebellion ends the same way but with differences being that Everyone except Homura isn't a magical girl anymore, and If you ask me, everyone living normal lives and no longer being magical girls seems like a pretty damn good outcome.
The reason Madoka was depressing was because of the TV series, lots of dark shit happens there. Rebellion's tone is pretty contrasting to the original series if you think about as well, during it's second half there was always this feeling of hope and things were getting better and better where the TV series was just a downward spiral with things getting worse and worse.