I don't like using the term "Cafeteria Catholic" because it somewhat denigrates legitimate anguish and confusion that many may have about some aspect of the Church's teaching and their own belief. It's a useful shorthand term however, so I use it to get your attention. For those who have not heard the term it refers to Catholics who accept or reject categories or specifics of the Church's teaching, just like they would take or reject some things at a salad bar.
People who do this "Cafeteria Catholic" philosophy of deciding on their own that some parts of the Church's teaching are "OK" and some are "wrong or out of date" are in serious error. However, they make it harder on themselves by seeing themselves as God's "editors" (which they are not) but also by not understanding God's mercy and that everyone is in the same "sin boat." Because everyone is a sinner and flawed, prone to temptation, this is exactly why the Catholic Church's teaching cannot be modified, because it is the gold standard of God's truth, period.
What these past two generations have forgotten is how to pray for belief and greater understanding while still holding portions of disbelief. This is explained in the Gospel, the Apostles and Christ all speak to this problem, as have generations of saints in their prayers and writings. It is "OK" and part of the human condition to hear the message of the Catholic Church but in one's heart doubt some part of it. Let us use the extreme example of abortion. It is part of the human condition and "normal" (hence "OK") if a Catholic believes all of the teachings but has in his or her own heart reservations and doubt about the Church's prohibition against abortion. The person may have doubts that are so severe that they have engaged in abortion or enabled the providing of an abortion and rationalized it saying that the Church is "wrong," "unequal," "out of date," "lacks understanding," or "just plain old mean." I have a news flash. You are not the first believer of any faith to have a problem with one tenet of the faith. But here is what is forgotten. You are supposed to work on this area in prayer and discernment to try to understand why God, not the Church but God, has created this prohibition. God is not sitting there with his finger on the hell trigger while you are having this discernment.
What is expected is that you are sincere in prayer and trying to understand the Church's teaching, and that you do not propagate your doubt and disbelief like a virus. It is a very simple two things to ask in return for God's infinite patience and mercy. I can guarantee that if you doubt the Church's correctness on abortion, yet are prayerful in trying to understand, trying to improve your discernment, withdrawing from any actions that promote the cause that you are having doubts about, and not spreading your doubt, especially among the youth whose faith is still being formed, you are not in an unresolvable conflict with God.
Many, many, many people have doubted one aspect of the Church's teaching or another, but the difference is that pious ancestors of today's people actually used that as a point of prayer to increase their faith and understanding, not to argue with God AND promote the very thing the Church prohibits! So you "believe" in the right to an abortion yet think you are otherwise a good Catholic? Then why are you not daily praying for enlightenment and understanding as to why God, through the Church, prohibits abortion? Why are you not adopting at least a neutral "do no harm" stance (taken from the Hippocratic oath of doctors) while you discern? In other words, converse with God in prayer, but stop advocating against him in your words and deeds. You do not need to confess during Penance, unless you wish to, that you have doubt about something the Church teaches. It is not a sin to doubt, it is part of people's human condition. But it is a sin to take your doubt and market it far and wide, leading others down your own temptation (the specific sin is that you are putting yourself before God). Many people only come to full and complete understanding of the Church after decades of prayer on this one particular point. That is a good thing, because it is another illustration of God's mercy and how he never gives up.
Sometimes it takes time and maturity ("growing up") before someone can understand the fullness and complete context of the Catholic faith. Even after twenty or thirty years a Catholic might look around at society and say to him or herself, "Oh my God, so that is why God prohibited this particular thing. I never understood before." Children are the most prone to being warped by neglectful irreligious parents and caretakers, while young people are the most prone to being tempted by self gratifying propaganda. Little children want to do the right thing but are often born into warping conditions. Teens and young adults want to do their own thing, and so they look for people who enable them. This is why it is extremely sinful to promote your personal area of doubt in faith among the children, who are innocent and malleable, and young adults, who are at the height of their temptation risk and often at their most defiant stage of religious life. This is why early Christian (just as Jewish) society provided complete and firm religious instruction from the youngest onward. They need the safety net of knowing the fullness and truth of the total faith. Temptation will lead them away on enough points without you and your doubts enabling this damage.
So trust me, God knows your doubts and understands. You do not have to dig around and find the mote in your neighbor's eye to justify, "Ha, I'm not the only one who disbelieves some part of the Church teachings." But the error is that thinking the Church needs to change for you. And the error is that thinking it is a hopeless impasse. The man told Jesus, "I believe, help my unbelief." Jesus didn't say, "Well, get out of here, unless you believe 100 percent you are no good." BUT he also did not say, "Oh, what part don't you believe of God's truth? Oh dear, sorry about that, we'll just update and edit that inconvenient part right out for you to make it easier." The whole point of that passage is that everyone needs to believe and then PRAY and turn to God to remedy the part of you that does not believe.
One final point that may help. You may wonder what happens if you firmly do not believe in one part of the Church's teaching, and die still holding that disbelief. You might think you have a chance to "argue your point" with Jesus. That's not actually what happens. When you die you receive through God perfect knowledge of the truth and the implications of your actions, and the "why's" of what God allowed and what God proscribed. So you never get to "argue" your case because you instantly see through God's eyes the entirety of the subject. You find out why God is "right" and you find out the consequences of your doubt. If you have been spreading your doubt to harm the faith and purity of others that is going to be a very bad thing, I'm not going to sugar coat or lie to you about that. If you have a genuine mental block due to some harm in childhood or other circumstance, you can expect mercy if you have been working on that through prayer. But there is no "dialogue" or advocacy for your doubtful stance because once you encounter the Christ you immediately understand what God has affirmed and required of all people. Your doubts disappear as if they never happened, because now you understand, but remember the deeds that you did with that doubt live on after you with people who still live. I strongly suggest minimizing the impact of your doubt on others since that is what you will be judged on, most truly and surely.