Modern unions that only represent one type of skill or workers in one company (or both!) are far less effective than historical unions that aimed to unionize as many workers as possible under the same umbrella. Being able to represent your members even if they switch companies gives you a lot more opportunities.
Unions are (at least supposed to be) democratically run, so if tech workers don't want to sit in the same position for 45 years until they can collect a pension, their union doesn't need to negotiate for that. They can use that leverage for something else.
Putting that together, your modernized union might be an industry-wide organization that acts both for collective bargaining and as a placement agency. They could bargain for making switching companies easier - maybe employers need to support specific benefits providers so workers don't need to switch. And they could use their network to improve bargaining - a big part of strike preparation is making sure everyone is taken care of ahead of time; the union could secure job offers for workers who can't afford to go on strike.
That's the difference between a craft union and an industrial union. A long time ago, there was the American Federation of Labor, the group for craft unions, and the Congress of Industrial Organizations, the group of industrial unions. The AFL had the Plumbers, the Electricians, the Machinists, etc. The CIO had the United Auto Workers, the Steelworkers, the United Mine Workers, etc. They merged in 1955.
Nobody cares much about that any more.
If you want to see a modern union, check out The Animation Guild.[1] Local 839, IATSE. They represent most of the major studio animators in Hollywood. Although they've tried, they have not been able to organize game developers.
It's about fear. Try to organize a union in the US and you will probably be fired. Even though that's illegal. WalMart has closed down stores that voted in a union. Uber workers have a strike scheduled for July 15, but it probably won't do much in the US.
Unions are (at least supposed to be) democratically run, so if tech workers don't want to sit in the same position for 45 years until they can collect a pension, their union doesn't need to negotiate for that. They can use that leverage for something else.
Putting that together, your modernized union might be an industry-wide organization that acts both for collective bargaining and as a placement agency. They could bargain for making switching companies easier - maybe employers need to support specific benefits providers so workers don't need to switch. And they could use their network to improve bargaining - a big part of strike preparation is making sure everyone is taken care of ahead of time; the union could secure job offers for workers who can't afford to go on strike.