No, if users didn't like anything they see on Facebook, they'd log off. Facebook optimizes to make money and they can't make money if people leave, so they try to avoid that scenario.

But that doesn't mean all content is something people want to see, because Facebook can't make money either if users only consume content that doesn't make Facebook money, so they try to avoid that scenario.

The profit-maximizing strategy is to show users a mixture of content they like (to keep them around) and money-making content, preferably all jumbled together so people can't easily tell the difference. (The same calculation is behind Google deemphasizing the difference between paid search ads and actual results.)