This income exists in the UK for contractors.
$150k/year is a day-rate of approximately £500/day if you take four weeks off per year. This is slightly higher than the median but reasonably achievable (more so in London).
Getting yearly fixed term contracts on £500 a day is also not easy even with the former.
You also lose your pension contribution which in the UK can be upto 25% of your salary (I’m on 24), ISA, insurance protection against dismissal with no cause and many other things that employers provide.
Contracting isn’t a solution it’s worse than at will employment and the OP is right outside of a few cases the salary in Europe is pitiful and the safety net does not cover anything really it only ensures that there is almost no social mobility upwards.
Europe despite having the world’s largest social redistribution event aka WW2 is still the mother of all old money and isn’t changing because outside those who in the US would become billionaires it’s nearly impossible to become financially independent in Europe as a salaried employee and even as a sole trader.
It's the opposite. It allows unlimited immigration from the EU. The people voted against that it's true, but the government ignored the referendum and implemented a local worker preference instead. But with unemployment very low anyway, it is easy to argue you could not find a Swiss person to do the work, so this is effectively the same as doing nothing.
The 7000 contingency limit clause for EU citizens has been triggered, and we know how the last referendum went. Foreigners are a burning topic. Try getting a B-permit from outside of Switzerland; it’s akin to winning the lottery. Whoever got in, got in. The way is shut, and the Swiss keep it.
I agree that immigration is a hot topic. However I'm not sure what difference more referendums will make if the government feels free to ignore them. Perhaps they'll have a change of heart.