The mantle being more important than the character seems to only apply to T'Challa now a days. Can you imagine if WB/DC had announced that the new Batman movie wasn't going to be about Batman and said that the franchise had always been about Gotham and not him. At least Batman being their cash cow ensures he'll always have a presence across media. After too many years of franchise mishandling T'Challa will never get that status especially when the film side moves forward with Shuri or whoever they make BP.
I guess we can also say goodbye to T'Challa in future shows. Once BP Shuri arrives in the MCU he'll likely be sidelined in favor of her on the animation side and maybe videogames.