Being public and having an advertising model will not allow for a truly free service. No way around it. Nor should one person be in charge of all content decisions.
Elon made a show of saying if Twitter fails because marketers pull out then it will be their fault. But wouldn't it really be his fault for relying on them to start with? Obviously he's not going to let it fail without a fight, hence the premium subscription model, but is he going at it the wrong way?