> How do you describe in a legal way the difference between a useful feature people want and an addictive feature they don’t want?

For laws like this it always boils down to "I'll know it when I see it" which is such a shockingly poor way to write legislation that I'm flabbergasted it doesn't immediately fail any amount of rudimentary scrutiny. Not to mention the latitude it grants for selective enforcement. It's basically Washington asking (through the Economist) for a leash on platforms that host their critics that they can yank at any time the population gets too rowdy, with the convenient justification that the algorithm is too good and our attention spans are in danger or whatever.