I agree and echo many of the posts above: it is not the job of the Tonys to make sure diversity is represented. That is for producers and casting directors to make sure Broadway has room for many different types of stories to be told. The Tonys bestow awards and nominations for stellar work, not because of someones race or ethnicity.
While this season would appear slightly less diverse, just look at all the worthy non-white actors up for nomination:
Eva Noblezada, Jon Jon Briones, Nicholas Christopher, Condola Rashad, John Douglas Thompson, Carra Patterson, Andre Holland, Michael Potts, Corey Hawkins,Rebecca Naomi Jones, Amber Gray, Denee Benton, Caesar Samayoa, Rodney Hicks, Anthony Azizi, Corbin Bleu, Michelle Wilson, Phillipa Soo, Barrett Doss, Kristolyn Lloyd
Is it as diverse as last year? No. The leads for straight plays are all white with the exception of Corey Hawkins. Which is unfortunate. But to the original poster's point, its highly unlikely that there will be an all white nominee list.