A couple of things as I understand them:
The Technical awards, sound and such, are nominated ONLY by people in their union so only the people in that field vote on the nominees. But the full academy votes on the category after the nominations have been made.
Seriously though, and this has been a controversy for years. The members, actors, directors, writers etc don’t necessarily vote. Or don’t vote in all the categories. Or even have seen all the movies. They give the ballot to a staff member, friend, or family member who is interested in voting. But gosh know if they have seen ANY of the movies.
But nothing can be worse than the Golden Globes. The TV network makes it sound like a big deal, but no one knows, or cares, who votes there. And it’s all foreign voting, nothing from the U.S, But it is promoted as if it was a prestigious award.
In the Tony awards, awards for Broadway shows, the people who vote, MUST show ticket stubs the the plays nominated as proof that they have seen them