Could it be that the real reason John XXIII suppressed the ancient Feast of the Circuмcision of Our Lord was because it implicitly rejected ecuмenism, pluralism, and the ecclesiological revolution he was planning to commence two years later?
Recall that the circuмcision was the mark of God’s once-chosen people, indicating they had been set aside from all others, as the only ones set upon the path of salvation.
Only those who bore this mark were part of (the precursor to) the one true Church.
A feast which highlighted exclusivity, rejected pluralism, and opposed the very spirit of the new ecclesiology would stand as a rebuke to the revolution being planned.
Very convenient, therefore, to replace the ancient Feast with another.
And after all, what kind of Catholic would object to a feast of Our Lady?!