Real life isn't that simple. These things aren't binary, "it's true" or "it's false". There is a continuum along which things vary. The extent to which companies are compelled by market forces to treat their employees well is obviously something that varies by sector / geography / profession / etc.

I'm not saying that nobody is justified in joining a union, or that unions have no reason to exist. I'm just saying that relative to my combination of the above factors, I do not find any appeal in the idea of joining a union, when you balance it against the associated negatives.