No kidding is right.
Lots of religions have beliefs that parallel Scripture. Having a belief that parallels Scripture is no great accomplishment. All it does is prove that sometimes other religions get something right.
Satan knows that he's not going to get his best mileage out of outright lies. That's why there's truth mixed in with everything he lies to us about.
It's far more effective to mix truth in with the lies than to lie outright. People can see the outright lies immediately. Sorting lies out from truth is often more difficult. And that's where Scripture comes in. It's the standard by which truth is measured.
We are commanded to test the spirits to see if they are from God, and the ONLY thing we have to hold up as truth and the standard by which to measure anything, is the Holy Spirit, God breathed word of the living God.
The subtle changes and additions to truth and what the gospel really says is Satan’s way and the RCC has mastered the technique.