Saying "society is just individuals" is reductive to the point of uselessness though. People exist within a system of social and economic realities, and the choices they make, indeed the choices they can make, are shaped by that system.

And therefore, many choices which would improve society only make sense as collective choices. An individual deciding whether to delete their facebook account is deciding between privacy violation or social isolation. In that context, the privacy violation might actually be the better choice for the individual.

When people criticise that choice, they're noticing that collectively it would be better if everyone made a different choice. But it's pointless to blame individuals for not making a collective choice. If we actually want people to make that choice, we need to act collectively, and transition away from facebook in a coordinated way.