Initially the algorithm is a reflection (or amplification) of our existing behavior. But at some point, that reflection and amplification causes it's own ripples.
So, the Beyonce fever becomes pitched in large part because of algorithms suggesting that content. I don't think each of those tweets would have happened independently.
The critique is that we're being fed so many suggestions that we don't have room to find out for ourselves what we like or want to talk about. Instead many times we're simply responding to and consuming the recommended content.
So there are people at the wheel, but the majority is along for the ride.