Maybe there are special requirements for such highly resolving portraits but I too see no real need for 98% of portraiture. 24MP is 4000x6000 pixels and if you accept 0.25mm dot size in the final product this is a 1 x 1.5 m printout.
I too use the R6ii for other types of photography: What I like is that the R6ii fills each pixel with valid information so you have 24 million real pixels - no recording of imperfections of lenses or sensor readout.
Another advantage is that older lenses perform perfectly in the range of the sensor resolution, so no storage of unnecessary pixels without real information - I have seen that you have the EF 1.4 50 - while not up to modern standards it is good at 1.4 and stellar from ~ f/4 onwards. Finally bought it after waiting 20 years for an IS variant with a little bit more contrast at f/1.4