That said unions help more than they hurt, in my opinion. It's also pointless to paint all unions with the same brush like that, you worked with a group of people that had bad management. That's can happen in any organization, not just unions.
Not they're not all great all the time but I think the Hollywood unions are something we as tech workers could model ourselves after. You still negotiate your own salary and such but certain benefits like pension/retirement/healthcare (which are great at scale but hurt employers and employees at smaller businesses) can be amalgamated across the membership.
Like for example just a couple years ago the writers unions got into a spat with their agents over double dipping with production companies and not representing the interests of their clients. That kind of bargaining power can be wielded to fix institutional problems across an industry, but it doesn't have to come at the cost of individual gains - the writers still negotiate their own compensation and sign their own deals.
Unions can be a great way for industries to self regulate imo.
That's a guild, not a union. And sure, it's good. As long as you don't care about people that aren't in it right now. SAG does their very best to keep new entrants out.
And they don't work to keep new entrants out. Union workplaces do prefer to hire union members, but if they can't then they'll work to get someone enrolled in the union.