It's mostly anectadata from where I live in the UE, but unions can facilitate/enable abuse: for example once you're an union rep, you can't get fired, so at my previous company, being a rep meant you'd get two years where they could do nothing and be protected by their status. In that company, no negotiations between the unions and the company never went anywhere, since the multiple unions could never agree on what would be acceptable or not, with some unions looking more interested in just membership numbers that anything else. Another I've heard was that unions would cover for employees that should get fired for gross misconduct.

It's cool to have the worker protections laws here, but sometime it feels like unions are just useless/wastefull relics.