I'm from Europe and I don't find unions particularly attractive, especially when they want to function like guilds, as they do in my country. That's basically gatekeeping and they want to have the power to specify salary ranges based on qualifications (e.g. university degrees, certifications, etc). A lot of people in the tech community are self taught and don't always take well to the idea that the only way to prove your worth is with a piece of paper they'd have to pay for.
In my current situation (UK) I have all the benefits you mentioned with none of the drawbacks, especially not the salary $60k salary cap (which I think is a misconception since some jobs I looked at during the whole Brexit fiasco were in Europe and paying closer to €90k).
I don't know about unions in the UK, but in some other European countries your union won't have anything to do with your salary negotiation or setting industry-wide salary ranges.
They might if you're in a teacher's union, or working in some minimum-wage job with a mandatory union.
But for any high-paying position like software engineering your union is there to have your back if you're being screwed over on your employment contract, to bust the balls of employers who worked you for 41 hours, but only paid out 40 etc.
It's essentially a form of collective employment insurance for your industry, for which you'd pay a small monthly fee.
In my current situation (UK) I have all the benefits you mentioned with none of the drawbacks, especially not the salary $60k salary cap (which I think is a misconception since some jobs I looked at during the whole Brexit fiasco were in Europe and paying closer to €90k).