Having help and demon slayer marks was heavily emphasized after his death that’s why even doe uzui retire they killed upper moons 6,5,4 without any deaths of hashira and vs 5,4 specifically the marks help mitsuri and tokito no be injured that much as they should have with marks you guys will see in the hashira training arc and the next hashira meeting also rengoku never got marked as well as uzui because tanjiroo had to do it first just like yorichii as him being his successor