Legitimate interest can be for anything (user, business, society as a whole) but it's still highly questoinable whether sharing peoples PII for ads alone is a legitimate interest (It's not clear it isn't either - the text is deliberately vague). What's clear is that you can't show people "by entering you accept to". You have to show them an opt out and if they opt out they need to get a service that is as good as if they opt in. Binary choice shouldn't help - if that has been a judgement it's very dubious imho.