You mean because of Freedom of Speech? I think it’s not that hard; your freedom ends where someone else’s freedom begins. Propaganda and advertising for example are designed to force you into believing something / thinking in ways that you wouldn’t, so you are effectively cut off from thinking and believing like you would have been doing without that pressure.

That probably depends on which constitution you're talking about ;)

But I wonder if "for-profit organization may not use recommendation algorithms" would be constitutional in e.g. EU countries.

An independent NGO or watchdog kind of regulatory body staffed by psychology and technology experts with the legislative teeth to issue cease notices with meaningful fines to back them up (take the GDPR penalties as inspiration) should a media platform implement a harmful user experience.

It would be important that the organisation is protected from lobbying interests and direct control from the elected politicians. Though obviously its existence would hinge on the corresponding legislation being persisted.

The result will be a couple of big fines and then everyone else will play ball