The local (national) councils of bishops have jurisdiction over the establishment of holy days of obligation. If the pastor at the parish in Switzerland told you that the feast of Mary the Mother of God is not observed as a day of obligation, then he is most likely telling you what the council of bishops has decided.
On a further note, I found this morning in the new calendar issued by my parish in the US, a list of no less than 17 Marian feasts on the liturgical calendar. Three of these are holy days of obligation in the US. We celebrate her parents for doing a good job raising her; we celebrate her conception and her presentation; we celebrate the announcement that she will bear the Messiah; we celebrate her visit to Elizabeth, her delivery of the Messiah and her membership in the Holy Family. We celebrate her assumption into heaven and her Queenship (of the Universe, Angels, Martyrs, Apostles, Saints, etc.). We celebrate her various apparitions at Lourdes, Lasalette, Fatima and Guadalupe. We celebrate her for her sorrows and the rosary. We also celebrate the dedication of the church dedicated to her in Rome (St. Mary Major). You would think that two or three celebrations would suffice but we get at least 18 by my count and two months dedicated to her (May and November). My biggest beef is that the Curialist had to steal Jesus’ Jewishness (Bris or circumcision) in order to put Mary the Mother of God in at January 1. Give me back the feast of the circumcision; we have more than enough Marian feasts.