Speaking from a completely meta perspective. Of course the ninjas are white, if it wasn’t for the fact that they were Lego characters they would’ve all been white with the exception of Wu.
But it’s because of the very ambiguous art style that Lego characters have that people have been able to create their own interpretations of how the cast of characters look. It’s honestly kinda cool to see how different people view their favourite characters. Some people interpret a character to look like themselves, others just have head cannons about how they think a character should look based on other factors. Sky is the limit with these little Lego ninja and there’s no wrong answer when deciding what they would look like.
Whether or not this new live action movie makes the entire cast white, or if they try to mix it up a bit with a more diverse cast it will always feel wrong. The true reason why a live action Ninjago movie won’t work is because it limits the way the audience can see these characters, by giving them a supposed “real” look it makes them feel less relatable with the audience.