We can argue about whether data-driven ads work for the OP or for buying an extra mattress, but in aggregate they absolutely work. Contra OP's anecdote, if FB a

We can argue about whether data-driven ads work for the OP or for buying an extra mattress, but in aggregate they absolutely work. Contra OP's anecdote, if FB ad targeting stopped working, then FB would notice the difference in engagement within a day - probably within the hour.