When one already has a rim brake frame, whether rim brake CF wheels are obsolete is beside the point; the more relevant question is how much one would be willing to spend on CF wheels for that frame.
I ride FFWD F4R FCC (CF) wheels with SwissStop Black Prince pads and see no noticeable difference in braking distance compared to Mavic Ksyrium Elite (alloy) wheels with Shimano R55C4 pads. However, brake modulation is definitely worse because the initial bite is a bit grabby, which took a few rides to get used to. (Continental GP5000 tires on both wheelsets.)