Assuming that unions are actually bad for the economy at face value
Is union is doing wonders for the officers and teachers the actual workers ? Making sure their rights and preferences are catered to ? Then the union is doing it's bloody job.
If you are an employee at big co that is abusive or exploitative earning minimum wage then the government has already abandoned you . Should you then see the wider societal implications and scarifice your needs for greater good or actually say fuck that and unionize and try improve your quality of life and not have to pee in a bottle during work,(Amazon) or catch COVID-19 and die cause your company doesnt care (meat packing)?
Even if it is bad for the economy/society unions still have been good for the actual workers as a group. We still have lot of work related deaths, long term issues and basic hygiene requirements missing, you absolutely need unions.
The competition is not with low paying jobs in cheaper areas of US or cheaper countries like mexico or china. It is with automation and robots, you can't compete with that. Without strong worker representation employees of unskilled workforces like Amazon are going to face worsening conditions in the future as they are made to compete with automation