The only valid space for it is Floatplane, which does full 4k support for all its creators - But floatplane is their own creation, so its just more on the ego pile.
That being said, the black magics aren't nearly as egregious. $10k for a good production camera is not really all that big of a deal, thats two months cost for a mid salary employee (Canukistan employment taxes are brutal). The 12k is only a grand a pop more than their bottom tier (A 4k as well), and as mentioned it can offer some editing benefits for when your crew is retarded and can't aim the camera very well.
The REDs were just a stupid ego trip, which seemed to have been an effort to make content from them. I don't think the RED videos did particularly well, at least not outperforming the usual random slop, and cost a small fortune. No surprise they'd walk away from that.
Still, I don't see 4k taking off for major streaming consumption anytime soon. Simply put, its too expensive to serve. Floatplane tries to get around this with their subscription model, but really its just burning money for marginal benefit, 4k's additions are mostly lost to compression hell. And streaming 4k raw is a pipe dream.