Are you saying that you don't honor the four Evangelists who wrote the Gospels? That doesn't make sense to me, because of many Protestant held views regarding sola scriptura.
I'm not here to argue about the attributes of St. Mark. In reading his Gospel I know that his words are inspired -- hence he was chosen by God and blessed accordingly.
Of course I respect him and his contribution. However, the Catholic church's proclaiming of "patron saints" is not biblical in nature.
As for "feast days," I would imagine there are enough patron saints by now to have thousands of feasts every year.