> Those legal protections are easily eroded without unions.

That's very clearly not true based on the situation in Western Europe, in fact legal rights tend to keep increasing even when union membership is decreasing (e.g. UK, France).

As said, jobs and society as a whole have evolved and noone can be elected in government by promising to take away important protections, what they can be elected on is promising to curb union power but that the unions' fault when they abuse striking action.

My understanding is that workers are extremely well protected in Finland and what's happened is only some restrictions on political and solidarity strikes.

Edit: Unions are not the only defense that workers have. We have democracy with all sides represented and nowadays (in Europe at least) more is done through elections than through unions. That's why I said that society had changed compared to the early days of the labour movement.

I just gave you an example. How can you say it is "very clearly not true".

You would have to somehow disprove the reality of what has already happened in order to make that statement