Outside of dedicated leftist groups like this one, every single person without exception that I talk to who is not in a union, and some of the people who are, say that unions are not needed anymore, that it's an idea whose time has come and gone, that there's this problem or that problem with unions, and the ones who have been in unions typically have no end of examples they can use to support this. When you point out that the Owners are worse, that they've taken more, ripped off more, and so on, it falls on deaf ears because the programming and indoctrination is simply that strong. I know someone who stays as a nurse at a hospital she hates with management she hates chiefly because the other nearby hospital network has unionized nurses. I know others who've worked in grocery and retail unions and has nothing good to say about them.
If you want unions to be accepted, you need one that will be a shining example, one that will get people to sign on to the idea of unions, one that isn't afraid to snub the political bosses and not be a pawn, one that treats its workers fairly, where anybody has a voice, and one that isn't afraid to fire shitty workers. Without that, give the fuck up now because it's never going to get any traction.
I think we'd get a lot further by encouraging more ownership of companies by the workers therein, like cooperatives, where it's more of a syndicate. Then you don't need a union to protect the workers from the owners because they are the owners of the company, and the workers are not chattel slaves. There are numerous examples of modern functioning cooperative companies, we need to be publicizing these and doing everything we can to support them and participate in them.
For companies too large for cooperative ownership to work (at which point I personally tend to think a company has gotten too large period), we need to fight for higher wages for workers and a cap on executive salaries. I think fighting for higher taxes is a red herring because the wealthy will always find ways out of paying higher taxes on their bracket, and if you pay the working class more, then they move up in brackets and they also spend more (so that's sales taxes as well), save more, and pay off more debts. Additionally, it's hard to argue for higher taxes for the wealthy simply because they use their media outlets to paint it as higher taxes for everyone; compare that to arguing for higher pay for the workers. Bring down the income disparity by bringing the bottom up.