Should I replace "backstab" light switches?
95% of the time, backstabs fail "open" - they seem pretty good at that.  That's not a fire starter, but it is an annoyance that will send you on a day-long "bug hunt" for the faulty connection.

The other 5% of the time, it will create a weak, overheating connection or a series arc fault, and yeah, that'll start a fire.  

The main reason we recommend scourging them is the future annoyance of a failed "open".