Entirely depends on what the goals of the union are. If you want to improve your position in search rankings, a union is not going to help you. If you're a youtube creator who wants a larger cut of advertising revenue, a youtube creators union may make sense.
I find it unlikely that there's any issue that cuts across all of Google's customers (advertisers, publishers, cloud users, gsuite users, etc), so a Google Customers Union probably does not make sense.
I find it unlikely that there's any issue that cuts across all of Google's customers (advertisers, publishers, cloud users, gsuite users, etc), so a Google Customers Union probably does not make sense.