Getting back to the op, is the Catholic Church apostate, maybe here is a way to look at it. While our Savior was on the cross, the spiritual and physical agony were beyond our imagination, especially when God the Father turned His head on His Son and Christ cried out "why has Thou forsaken Me?" Surely much went through His mind.
Pure speculation, but it would not at all surprise me if the RCC, which would be founded several decades later (depending on which fairy tale one believes), and how dominate that "church" would be for centuries to come, sometimes the only established church, went through our Savior's mind. In fact, I would go so far to say it caused a good bit of His pain. Apostate is not the word, if there is a stronger one, to describe the pain Christ felt for the damage, the trail of ruin, the evil, the worldliness, that this cult would do to telling others about Jesus Christ throughout the centuries. The false doctrine, the alliance with evil governments, the murders, the torture makes organized crime look like a Sunday School.
For whatever reason, God used the RCC to shape His purposes. He preserved His NT church with the weakest, most isolated churches of the day. There were no elaborate buildings, riches, Popes, or other such nonsense. When God carries out His plan with the least likely to succeed, the honor and glory goes to the Lord, as it should.
The way the posts of the Catholic Church are worded, one makes it sound like it is a holy organization that made a few errors along the way. It is nothing of the kind. The Catholic Church is not on the edge of orthodoxy as someone said, it is the essence of pure evil. Worshipping created being, teaching a salvation of works, and breaking every commandment in its relation to the established governments of the day.
As Jesus Christ said about His church, "and the gates of hell shall not prevail against it," the RCC is the gates of hell.