“Unmarried girls going to the Mikva (better that way than not, but still bad)”
Not according to the Kitzer Shulchan Aruch, who paskens that girls and boys should all go to the mikveh Erev Yom Kippur starting at age nine.
But overall your point is well taken; it is important it is important to distinguish between the many kulot that have halachic support, and kulot that are made up.