It’s the Catholic Church and it’s apologists who readily admit they have incorporated paganism.
Indeed.
John Henry Newman
In a later age the worship of images was introduced [Note 11]. {371} 4. The principle of the distinction, by which these observances were pious in Christianity and superstitious in paganism, is implied in such passages of Tertullian, Lactantius, and others, as speak of evil spirits lurking under the pagan statues. It is intimated also by Origen, who, after saying that Scripture so strongly "forbids temples, altars, and images," that Christians are "ready to go to death, if necessary, rather than pollute their notion of the God of all by any such transgression," assigns as a reason "that, as far as possible, they might not fall into the notion that images were gods."
...the rulers of the Church from early times were prepared, should the occasion arise, to adopt, or imitate, or sanction the existing rites and customs of the populace, as well as the philosophy of the educated class...
In the course of the fourth century two movements or developments spread over the face of Christendom, with a rapidity characteristic of the Church; the one ascetic, the other ritual or ceremonial. We are told in various ways by Eusebius [Note 16], that Constantine, in order to recommend the new religion to the heathen, transferred into it the outward ornaments to which they had been accustomed in their own. It is not necessary to go into a subject which the diligence of Protestant writers has made familiar to most of us.
The use of temples, and these dedicated to particular saints, and ornamented on occasions with branches of trees; incense, lamps, and candles; votive offerings on recovery from illness; holy water; asylums; holydays and seasons, use of calendars, processions, blessings on the fields; sacerdotal vestments, the tonsure, the ring in marriage, turning to the East, images at a later date, perhaps the ecclesiastical chant, and the Kyrie Eleison [Note 17], are all of pagan origin, and sanctified by their adoption into the Church. {374}
The introduction of Images was still later, and met with more opposition in the West than in the East. John Henry Newman, An Essay on the Development of Christian Doctrine, Chapter 8. Application of the Third Note of a True Development—Assimilative Power; http://www.newmanreader.org/works/development/chapter8.html