Doubt it. Mentorship and apprenticeship opportunities are abound. Unions provide a floor for negotiations from which you can up-negotiate.
If your categorization was true, actors would never have breakout opportunities despite their union representation. Reality disagrees with your assertion and any movie star ever acts as evidence contrary to your claim.
Unions have personally screwed me out of hundreds of dollars of month in payment for pensions I'll never see because they've forced me into inappropriate position titles to the benefit of legacy members.
Good governance, fairness, accountability, responsibility, transparency remain challenges for all organizations, not just unions. Happily, we've been getting better at finding and learning from other experiments.
Reform is thankless exhausting work. It takes a special kind of crazy for a person to do that kind of policy work.