Kid was never and never going to be an equal and true rival to Luffy, safe perhaps during Saobody, but it's been made incredibly clear since the timeskip that Luffy would always be stronger and have a royal treatment that none of the other Supernovas could dream of.
Dressrosa comfirmed it with Luffy's defeat of Doflamingo after Law's failure to do so, and him getting his own fleet. Whole Cake Island was the nails in the coffin, and Wano is the laughing over the grave.