I’d argue that it’s knee-jerk reactions from negative-biased ”fans” (many of whom say they haven’t even seen the movie) that’s kept Wakanda Forever from making more money.
Maybe, without T''Challa, the film just became another in the long line of "Next Marvel Product" for many and it made little argument for seeing it. It's got some bump, but like all Marvel post End Game. What is the point? It's filler for a cinematic universe currently going nowhere. We may at some point get a movie in the future where the Atlantians, or whatever they are, rise up to help fight Thanos 2.0. Nothing more, nothing less.