We already do limit harmful speech, at presence it's limited to speech and will immediately cause harm (the whole "shouting fire" thing) and the demonstrable addiction properties can be reasonably shown as harmful.
It's also telling that only corporations seem to be the ones demanding the right to infinite scroll; what's the scenario where an individual can only express themselves and their ideas through implementing infinite scroll on a social media?
We draw lines in the sand all the time for the sake of public safety, I'd like to hear a specific case of harm here.
“Shouting fire” was a bad decision denying the right to protest the draft, and it’s since been overturned. (Thankfully, as we may need that right soon!)
The First Amendment is clear: there shall be no law abridging freedom of speech. Courts have bent around that in the past, in earlier eras, but they were wrong to do so. Their mistakes have mostly been corrected although there’s still a few left.
The document that governs this country spells it out: it can’t be done. Public safety be damned. There’s no public safety exemption in the Constitution. If you want it done, pass an amendment. There’s a process for it.
I personally dislike infinite scroll, but I dislike the camel’s nose in the tent even more. No speech laws.