For what it's worth, a full CMYK mode is on my personal to-do list after the final 3.0 release (though 3.0 RC has had CMYK import/export and soft-proofing for a long while). I made a prototype implementation earlier (https://twitter.com/CmykStudent/status/1618261982628704259) and with all the color space improvements made since, it should be even easier to prototype now.

Out of curiosity, what improvements in 3.0 RC are you skeptical of? If you're willing to share, it'd be helpful feedback for us. :)