I view the harlotry of the RCC as being cut from the same template as the spiritual harlotry written of in the OT.
The similarities are incredible, but in a broad sense they are summarized by: focusing around religious culture rather than personal relationship, and being driven by spiritualized legalism.
Oddly enough, Islam is cut from the same template. Religious culture/ spiritualized legalism.
This is why I point to a more ancient religion as being the one referenced in Revelation: because of the word "mother".
RCC and Islam are spinoffs (daughters) of the ancient distortion of God's Word.
This ancient distortion survives today, and thrives in global political positions, media positions, and corporate positions.
Both Islam and RCC are bad because they take after their mother, who wrote the Talmud, developed astrology, dualism/stoicism, and turned the heart of Israel away from God and towards the false god of Judaism.
The template for all major religions come from the precepts of Zoastrianism, which was adopted by many of the Israelites. The blend of Zoroastrianism and the Word of God creates Judaism. Leaning to the left makes one Kabbalah. Leaning to the right makes one Hasidic.
With this ancient root in mind,
it is not out of line to wonder if RELIGION ITSELF is the mother of all harlotry, in the sense that all religions are false
except true religion of giving selflessly (which is not a religion by modern standards, but a mindset and lifestyle).
Religion is man's attempt to systematize and control our relationship with God, rather than simply having a relationship with Him. All religion is, at it's root, humanism.