Indeed, that is the reason they adopted:
>Easter
>Christmas
>All Hollow's Eve
>The use of the Cross
Some more I don't remember
But, here's a reminder:
Jeremiah 10:3-5
3 For the customs of the people are vain: for one cutteth a tree out of the forest, the work of the hands of the workman, with the axe.
4 They deck it with silver and with gold; they fasten it with nails and with hammers, that it move not.
5 They are upright as the palm tree, but speak not: they must needs be borne, because they cannot go. Be not afraid of them; for they cannot do evil, neither also is it in them to do good.
also:
Deuteronomy 12:30-31
30 Take heed to thyself that thou be not snared by following them, after that they be destroyed from before thee; and that thou enquire not after their gods, saying, How did these nations serve their gods? even so will I do likewise.
31 Thou shalt not do so unto the Lord thy God: for every abomination to the Lord, which he hateth, have they done unto their gods; for even their sons and their daughters they have burnt in the fire to their gods.
Even if it was used to convert pagans, it is strictly forbidden to apply new customs and traditions to what was already teached in The Bible, thing that the Catholic Church has done.
The consequences of that are as follow:
Revelation 22:18-19
18 For I testify unto every man that heareth the words of the prophecy of this book, If any man shall add unto these things, God shall add unto him the plagues that are written in this book:
19 And if any man shall take away from the words of the book of this prophecy, God shall take away his part out of the book of life, and out of the holy city, and from the things which are written in this book.