The MCU has been going strong for over 15 films. Every single one of those films has been headlined by one of the same eight white male characters. Yes, Black Panther marks the first MCU film not only starring a black man but featuring an almost-entirely black cast. Similarly, 2019 will see the first female-led Marvel film in Captain Marvel. However, we've got to be honest here: the MCU should have started prioritizing diversity a long time ago.
Warner Bros., on the other hand, had a woman in a starring role by their fourth DC movie (and their third had the very feminine Harley Quinn ostensibly as one of the two leads). Their sixth film will star Jason Momoa, a Hawaiian, in its lead role. Cyborg, due out in 2020, will mark their first black lead, seven years after launching their cinematic universe and before hitting their ten-movie mark if it's released on schedule. And that's not even taking into consideration their behind-the-scenes talent, which includes female and Asian directors.
The DCEU has been putting diversity in the spotlight far more than Marvel. DC has also put diverse directors behind the camera; it took the MCU seventeen films to put a person of color in the director's chair, with Taika Waititi being the first. Diversity isn't a competition, but this is perhaps the single most egregious folly in the MCU's existence. It's gradually being righted. Yet, it's not a complaint we've really ever been able to make about the DCEU.