As always with these claims (that, as noted below, have not actually been implemented and so can only be speculated on), the question isn't whether this could be done with the blockchain, but rather whether this requires the blockchain to be done.
All too often the claimed magical things the blockchain will allow can be implemented far more easily with other, existing technology. So far it's a solution in search of a problem.
Nothing wrong with that.
The fact crypto is riddle with quick money making claims and project using the blockchain for sheer buzziness tends to make skeptics extra pessimistics in their views.
It's unfair to the technology.
We have a transaction oriented temper proof distributed transparent database.
Those are objective features, and they deserve we give them a try.
Full public transparency isn't that great a property of a voting system.
And it's hard to call it a "legitimate use case" before it's successful.
And come on, it's a highly experimental technology whise use cases impact the most controversial aspects of our society : money, vote, accountability, transparency, power to the masse.
Of course it's going to take time and fail in many spectacular ways.
The fact it's hard to not only implement correctly, but to promote to society does not mean it's not relevant.
Good things take time.
Remember that people thought for some time that general relativity and the Law of large Numbers would never have practical applications.