Ironically enough, this falls exactly into what Chadwick was trying to fight. He wanted to break away the concept that only one Black person can occupy a space at s time, well that's exactly what they are doing right now with T'Challa. No one else is allowed to play T'Challa other that Chadwick and since he passed, the character is being forced to pass with him.
This would make sense if it were a character like N'jobu. Say the character survived and was a fan favorite and poised to return for the sequel, however Sterling passed, it would make more sense for the character to go with the actor Because essentially created for a role that had no history behind it, N'jobu is a Brand new specific character created and exists soley in the MCU and as such is more easily able to retire. T'Challa however existed long before the MCU, before Chad, and has alot of historical Importance to him. Such a character should never be beholden to or retired with any one actor ever Because you saying the actor is bigger then the character and that the character is only as important as the actor who played them.