The fundamental, glaring problem of Roman Catholicism is how they've allowed corrupt doctrines to take root, contrary to the word of God. It's very stark, this problem of legalism, which is demonic in character:
1 Timothy 4
1 Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils;
2 Speaking lies in hypocrisy; having their conscience seared with a hot iron;
3 Forbidding to marry, and commanding to abstain from meats [legal bondages], which God hath created to be received with thanksgiving of them which believe and know the truth.
4 For every creature of God is good, and nothing to be refused, if it be received with thanksgiving:
5 For it is sanctified by the word of God and prayer.
It's a serious matter, these works salvation doctrines that diminish Christ and elevate man. Of course, it's a gospel that's accursed:
Galatians 1
6 I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel:
7 Which is not another; but there be some that trouble you, and would pervert the gospel of Christ.
8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
9 As we said before, so say I now again, If any man preach any other gospel unto you than that ye have received, let him be accursed.
There really is no dialog to be had between Bible believing fundamentalism, which subscribes to the faith of Jesus Christ and the apostles of the first century church, and Roman Catholicism, which deviated from the path of true Christian faith. The Bible believer and the Roman Catholic don't really share the same faith of scripture. You may as well be talking to a Muslim, which, incidentally, Francis prefers to dialog with, anymore. Is that not ironic? Ecumenicism with antichrists?
Roman Catholicism is an object lesson as to the importance of scripture, having fixed truth of the word of God, to measure our faith and its doctrines by. It was for this same reason Roman Catholics murdered fundamentalists and burned scripture, dared burn even the very word of God, before they were defanged. Scripture exposes the whole scam, and they couldn't have that.