> Why would a no-call list work well in one country but not others? I don't get it. At least explain what makes them work in Spain or Sweden if you are convinced they are the reason you don't get calls?

My parent (or parent-parent) comment made this clear, why a list in one country might work but in others not:

> I think in both countries these methods are supported by actual laws, one via "advertising-exclusion systems" that the companies need to respect, and in Sweden via the Swedish Marketing Act which forces companies to not call people who've "clearly objected to that method" or something similar. I'm sure similar laws and lists exists in other countries too.

If there is no law about it, and no enforcement, then obviously such list would work less effectively than in countries where it is supported by a law somehow, and it is enforced.

> I think what you have noticed is that the GDPR made it harder for legitimate companies to cold-call all over the EU

It has not, why would GDPR have an effect on the telemarketing companies, especially trans-EU ones? They're properly registered as controllers (otherwise they'd be shut down), and added more controls around the data they store. GDPR doesn't outlaw storing data, just controls how companies do so.