The problem is that strongly-held myths can still cause a lot of harm to others. While it may be understandable for people to cling to some myths, we should still work to stamp them out, but compassionately.
The book Sapiens covers this well, that you cannot escape the prison of a myth without being contained by one larger.
If one takes “myth” to mean something that is itself believed without being falsifiable, it is true by necessity of any belief system with any content beyond statements about the subjective experience of the believer