I was in the musician's union for 12 years before I got into tech. There were some silly rules, like someone couldn't be both a musician and and orchestrator on the same show, because it's "doing 2 jobs". It's like saying you can't be full stack. You couldn't fire people who were bad at their jobs and stopped putting in any effort. There was a profit sharing agreement that the union rejected, because it would come at the expense of higher base salaries, and then they wondered why there were only big producers that first developed the show out of town.
Some rules I actually liked. Rehearsals started and ended _exactly_ on time to avoid overtime (showing up late was the only reason you could be fired, which was a useful compromise). But generally, the union was the yin to the producers yang, and an adversarial position as worker advocate was where they wanted to be, they didn't want more ownership.
If someone gave me the chance to join something more like a worker-owned coop, where the workers on the business and vote on how it works, I would actually be down. There's a grocery store down my street like this and it's a great place. I don't know how this would actually work in tech. If there's no startup capital, no one will have a salary or benefits for years until there's a profit (if at all). And capital comes in exchange for ownership of the future upside.