I mean if you gave Project Soul the budget RDR2 has and also made them overwork 15h a day, I'm sure you could have a masterpiece too. But honestly the things you're complaining about are almost moot. The roster size is fine, yes it's missing 3 or 4 relevant characters, the rest was good riddance. I'll give you the stages and 2P costumes, but that's far from being the most important things in a fighting game. Like I said, I love me some CaS too and I'm bummed for the pieces, but you're still gonna see great creations anyway, all the features are still there. As for CaS styles, as fun as they were, good riddance, they weren't balanced nor was it realistic to expect them honestly.
The most important things in a fighting game is the offline content, the online aspect, and most importantly, the gameplay. This game has more hours of single-player than many Action and RPG games these days, the online seems decent enough too from the reviews, and pretty much everyone who's played it says this is the best the gameplay has been since SC2, so I'm not sure if it's just subjective anymore.
Again, it's your money, and I'm sure RDR2 is gonna be great anyway, but let's not cut SC6 short either, they seemed to have done their best with what they had, and they had to cut on the less important parts of the game. The fact that we have a Soulcalibur game coming out in roughly a day is a miracle.
