In this day and age, there’s zero excuse for not having diverse panels at writing cons. In every genre. (Yes yes everywhere but I’m speaking about writing cons specifically)
And as we get invites to appear on panels, etc, it’s on us to check out who else we’d be presenting with and if it looks exclusively white, bring it up. “I notice the panel looks very white. What are your plans to address this? I can recommend this person who’d be good”
And then to be willing to not participate if you don’t get a response you feel is genuine and will address your concerns.
I do know people in publishing who do raise the issue and sometimes to works and the panels are adjusted. Other times they get gaslit and treated like “a problem”