Self-segregation, so in-vogue nowadays. That, by the way, is also not the way to do things.
> No review process is more fair. But if you end up with all-X selections from a blind-review, you may be advertising to a very homogeneous culture. As a result, you may be limiting your pool of ideas to choose from and reaching only a local maximum. There are usually great non-X engineers, as long as you reach out to them. Mixing multiple varied-X groups usually results in more diverse discussions and ideas, in my experience.
Moving the goalposts, as usual for this kind of crowd. What would be your way to blame everyone but the people not submitting papers if you were told that the organizers did reach out as many different groups as possible? I know of several, I'm just curious to read which you'll use.
If we were discussing what-ifs, then I'd say - tough, maybe next year they'll have more success. But that's not the situation we're discussing. An organiser responded with "we can do better, we're postponing", so I don't have really a comment to that.
On the other hand, not caring about it and accepting that you're just getting dominant group X submissions is not a terrible thing. But we're social creatures - if everybody nearby is similar but different from you, either you'll feel uncomfortable, or have a bard-level charisma. So by allowing your group to become almost entirely X, you're enforcing the limit on your submitted papers pool even further.
(applies for many (all?) X, where X influences your life in any way)