Gengetsu can't end Naruto Six Paths meta but he can be a viable p1 if you are tired of Naruto Six Paths. Also, Madara Rinne can't end NAruto six paths as well because he will make it worse once he join Naruto in the same team and its more cancerous than ever. Remember when Itachi Edo is the counter for Kakuzu but players put them together on the same team? MAdara will make the NAruto meta worse.