All of the GLs are white or a big slug.

No one in this entire franchise is a human from Earth, so their in-world identities are completely irrelevant - Ahsoka being orange, Thrawn being blue, etc is not diversity. Paint is not diversity. There are no black, white, brown, yellow, pink or red humans here, because there are no humans. There are no Muslims, Christians, Jews, Hindus or any other religious culture. There are no Americans, Japanese or French and their accents are present only for the audience, to suggest species variety.

The only thing that matters from a diversity point of view are the crews' identities, and that solely reflects the Earth society at the time and place of production. Hollywood in the 70's was not culturally or ethnically diverse or feminist. White guys galore. Moving away from that is definitely a good thing (IMO). 

Including a diverse crew is not what has "ruined" the franchise. Having idiots in charge of management, writing and direction has. Having a racist audience that won't accept non-white heroes is probably a major factor as well. The actor is definitely not to blame. I would have loved to see Finn become a Jedi, not because he is black - but because the path from stormtrooper to Jedi would have been cool. But the entire sequel trilogy is just a poor excuse of a rehash, so he became Lando 2.0. Reva, Aniseya and Osha could also have been cool, with better character development. None of these character ideas were bad in my opinion - someone just ruined them. Even Rose, with a lot of rework, could have been...  decent?

We can't have a diverse GL until we have that particular flavor of diversity as a main character in the movies and TV shows. And we can't have that until we have a diverse and accepting society producing and consuming these movies. We are not there. Yet. So DEI is needed, but it needs to be done right - not shoe horned in by some crazy white Karens.