"Special" children ought to earn that distinction by demonstrating it, living it, making a difference with their specialness. If they are supposed to be smarter, more capable, with a bigger purpose, then it should be evident in their words, their actions, their impact.
If someone is dysfunctional, drags everyone else down, has no attention span, and rebels against authority, then it would be wrong to label them an "Indigo Child" just because they have some of the traits (all the bad ones). And if they or their parents then go around parading the Indigo status as a mark of specialness, you can tell it's done out of ego or denial.
You'd think an advanced soul would have better resilience against hardship, more empathy and understanding, and better self-mastery versus non-advanced souls. They would have more humility and just "be" it instead of announcing it. They would be a plus sign, instead of a minus sign, in the world equation.
I believe there's something to it, that the influx of souls changes according to historical circumstances. If we have a cataclysm and rebuilding coming up, then yes you would need a greater number of higher caliber souls to steer the transition. But at the same time, I think a bunch of different phenomena are being bundled under the Indigo label. Genuine 'special' souls with a 'special' mission could be part of it, but they're being grouped with kids who are dysfunctional, brain damaged, or psychopathic, or even alien hybrids seeded here to eventually become our new masters.