I wouldn't call the characters ROA made "abominations" if anything they're unique enough that I like em.
Alright, I really don't think half of the stuff you say here is accurate. Let me look at these one-by-one:
"I'm not saying they have to be competitors, I'm saying why should I play a mechanically inferior one, with characters I don't like, on stages that are bland, with generic background music?"
I see you're point in the first half(the underlined part) but to call the stages and music bland isn't really accurate.
Sure, the ost and design gets stale after awhile, but that's not that big of a deal considering this is a indie game, not a AAA game studio that can afford entire orchestras and hire people to design for them.
"Rivals of Aether and Brawlhalla are fine? They work? But when you compare them to their inspiration, they have nothing on it? It's literally the "we have Smash Bros at home" meme made into a game."
This is not true at all. ROA takes the classic Smash style gameplay and expands upon it via the combo system and stage design. The basic summary is that every stage has the same general layout(a solid platform with drop-offs on the side and a few platforms), just different things affecting and changing that layout. I don't remember how the combo system works off the top of my head, unfortunatly.
It's completely different to a game like, say, Bloodstained, where it's filling a void left by a dead franchise.
That doesn't mean that the game is quality thou? A game filling the void left by another /=/ good.
I.E., in my eyes, Rivals has no reason to exist. It's a cheap knockoff of a far better game.
So, assuming I'm getting this right, you hate ROE because it takes Smash's design, adds its own characters, and then expands on it, with no prior series or place to start from?
That's not very sound logic. And knockoff is a bit disingenuous, at the very least it innovates on the fighting genre, if by a little bit.
Regarding the "OC" issue, the main reason I love Smash in the first place is the characters that I already know and live interacting with each other. That doesn't exist when everyone already exists in this universe exclusively. The guest characters are cool, but they're only 2 out of 14, meaning I actively like two out of fourteen characters.
Alright, again, I see you're point in the first half(the part I underlined) but in order to forge that connection, you need to know the characters already.
"Why should I care about the OCs?"
So, if you care about the OC's, you can forge that connection and come to enjoy them. Everyone's journey starts somewhere, so at some point, you would have no knowledge of the Smash characters you love, and didn't have that connection. Learning about new things is just the way to start that chain of events to learn to like them.