The previous system never blocked scams because scammers didn't bother to check if your phone number was in the block-list before calling you.
That new law is not going to change the number of spam calls most people will get, as they're not from properly registered businesses.
Someone is paying for the number, make them responsible.
And if that is a company that offers service of lending number for such calls, they deserve to suffer too
It's not about scams, it's about commercial telemarketing calls.
Scams have been heavily hit in January when the French regulator mandated the telcos to implement a complete block of spoofed phone numbers (it's not an actual hard block, but unauthenticated calls will be market as "private number" which are ignored by most people already).
There will always be scammers who register an actual phone number to run their scams, but this rule will at least stop the constant phone harassment that made everyone unplug their landline phone.