The basic gist of unions (or "collectives" or co-ops), that they offer employees and workers leverage and collective bargaining power to counteract arbitrary changes, still stands as necessary.
I also have experience with public sector unions, and though management might dislike them, I know very very few employees who would choose to be non-unionized instead. It's literally giving yourself up to the whims of your employer for no gain.
> I get that corporate=bad, but do we want them to become more poorly run and inefficient than they are now?
Do we want them to succeed at the cost of basic human dignity, or by dragging people into shitty working conditions? "inefficient" for whom? That human dignity should come at the expense of corporate profits is, I think, always a grotesque position to hold. We can mitigate that out by understanding how profit can co-exist with safe and good working conditions for everyone.