facemaker329:
Looking at it from a different perspective...one of the hallmarks of Opera is the spectacle.
Inversely I don't consider "spectacle" to be a component of Space Opera or Sci-Fi... or really any particular 'genre', except Micheal Bay and JJAbrams, if you want to call their styles a 'genre' (which I do actually).
But that's because those two film makers are about the empty spectacle, it's all cinematics, no heart. By your metric, JJAbrams Star Trek movies are Soap Opera, which I'd disagree with (they aren't even 'Trek' in my opinion, but my opinion is my opinion).
I disagree with your assertion that Space Opera isn't about the distance between places. It is and it isn't. It isn't in the way 2001 is about the portrayal of distance, 2001 was aimed more at hard Sci-Fi, similar to The Expanse, despite The Expanse so very soft sci Epstein Drives and 'gravity drugs' to allow them to 'close the gap' between the Belt and Earth (weeks of travel instead of years), 2001 uses distance to showcase the hardship of space and our technological mastery at overcoming it. However Space Operas often have those 'slow moments' (usually a travel montage) where the characters can investigate their own motives, or 'wilderness' treks where they are cut off from "everything else' and can spend time on internal reflections. There is also usually a remoteness between places (sometiems deliberately to emphasize how someone is cut off form help, alone), the original Star Wars trilogy had this, then George started wiping it out with his remakes and the Prequels, but the "distance" still peeps through in places (even in the Prequels). The Sequels have no distance, everywhere is right next to everywhere else.
As for Firefly, the reason I don't call it Space Opera is the 'lack' of scope and the focus being different. While there is a larger conflict, and they do get drawn up into it (in the movie definitely), it's more in the way protags in Westerns do, reluctantly at every step (even fighting agianst beign involved), obliquely, and not from a position of control. The Firefly crew aren't trying to overthrow the Alliance (was it the Alliance? My lore is iffy after all these years), they were just trying to ply the trade out at the edge out where the Alliance's grip was loose and the Captain could 'fly free'. Which is why I call it a Space Western, the scale of conflict tends to be local, the scope tends to be personal, and the focus is more 'rugged individualism' rather than any spiritual/mystical journey (though I'll admit, my choice of focus might skewed as I tend to use Star wars as my 'primary' Space Opera template).