Or more likely, Canon hasn't cared enough to make it fast and treated it as a checkbox item "HDR? check!".[..] It's no different on jpeg or raw for processing time for HDR, it's just very very slow. I assume this is a processor issue not a sensor issue, so I would hope that Canon look at using third party sensors that are outpacing their own to keep up with this aspect of photography.
Back to the current state of things, someone on the DPR EOS R forum mentioned that a tweaked picture style can get you close to what your phone does, have you tried that yet?