Clearly, some feasts demand universal attention, times when the full Christian assembly gathers for Eucharist. Most notable are the feasts of the Lord, which is why Christmas and the Ascension command our collective devotion and attention regardless of what day of the week they occur. As any pastor can tell you, though, the feast of the Ascension has never commanded wholesale attendance when celebrated on Thursday. Given the feast's importance in the divine plan of things, the bishops of the United States have permitted dioceses to transfer the Ascension observance to Sunday, the Seventh Sunday of Easter. Some dioceses hold out for the Thursday observance (such as Boston) for a variety of reasons, including a reluctance to "throw in the towel" on weekday Mass obligation.
As the Boston site explains, "The feast of the Conception of Mary appeared in the Roman calendar in 1476. After the dogmatic definition by Pope Pius IX in 1854, it became the Feast of the Immaculate Conception." The date was set nine months before the feast of the Nativity of Mary on September 8. Given its doctrinal importance, and the fact that Mary is named Patroness of the United States of America, this feast is considered the primary observance of the Virgin Mary in this country and the attendant Mass obligation is not transferred. If the Immaculate Conception falls on Sunday, as it will in 2019, it is transferred to Monday, as the Advent sequence takes precedence.
This brings us to next Monday, the Feast of Mary the Mother of God. The feast and its title were universally established in 1931. At that time January 1 observed the Circumcision of the Lord as a binding holy day, in part because it was the octave day of Christmas and in part because it was the first day of the civil new year. With the new missal of 1970, January 1 was designated as the Feast of Mary, the Mother of God. However, Pope Paul VI also designated January 1 as World Day of Peace, and if memory serves me correctly, the early missals after the Council contained a Mass for Peace on January 1, to be used at local discretion. So, in my lifetime January 1 has been observed under three titles.
Now we enter the tricky business of designating which holy days carry the greater obligation. January 1, along with the Feast of the Assumption and the Feast of All Saints, are not considered days of obligation when they fall on a Saturday or a Monday as happens next Monday. Conservative publications point out the oddity of this arrangement, and I have to agree with them. I believe it was Thomas Jefferson who penned that bad law discredits all law, and I fear we have that situation here, To alleviate this peculiarity, the USCCB recommended that even when one of these three holy days falls on a Saturday or a Monday, pastors should schedule extra Masses to encourage the faithful to attend even when no canonical obligation exists. The last state of affairs may be worse than the first.
I can only say that if a thing is worth doing, it is worth doing well. And if we can't do it well, we might better be honest about it and bring liturgical law in line with actual piety, which as I read it states that the only time people go to Mass as a rule is the typical weekend and Christmas Eve. I'm not thrilled that the bar is set so low, but I think Jefferson (or whoever) has a point.