And you should.
It carries a prejudicial tone to others, and is usually associated with an attitude of “holier than thou.”
I know you did not mean that, and I know you do not carry such an attitude; now you DO know, so if you were to continue that would be wrong.
As an aside to everyone reading this particular thread consider how the Divine Liturgy ends, and the beautiful way Eastern Christians think of their parishes (emphasis mine):
May Christ, our true God, risen from the dead, through the prayers of His most Holy Mother, and of the holy, glorious and illustrious apostles, and our holy father John Chrysostom, Archbishop of Constantinople, and of Saint (N . . . whose church it is) and of Saint (N . . . whose feast it is) and of all the saints, have mercy on us and save us, for He is gracious and loves mankind.
Our parish church belongs to St. Anne or St. John the Baptist, etc.
In response to your initial query: Many parishes decorate for Christmas (including trees) ahead of time because there just might not be much time or help if you wait until after the 4th Sunday of Advent. This year, for example there is about one day to get that accomplished.
I pray your Advent remains calm, quiet and prayerful as we await the coming of the Logos, the Word of God who dwelt among us,