Opinion: The decision to separate CC from last-gen/PC and current- gen was made because they're locking CAW parts to The Island
This right now is just speculation on my part, and I really hope that's all it is, but I already suspected this could happen and the news they're dropping cross-gen CC pretty much convinced me to be the case.
So basically, like persona cards, you're going to have locked CAW parts that you can only unlock by buying them in The Island.
Not only The City in NBA 2K does that, and 2K has been following the NBA 2K footprints since the introduction of MyFaction, but they're already including "Island Cosmetics" in the different editions of the game like an Uncle Howdy mask and an OTC shirt.
I hope I'm wrong but I there's a good reason to be concerned until they confirm otherwise because I can't see any other reason they'd drop cross-gen CC and them introducing a City mode with cosmetics they're already promoting is just too coincidental for me