I just replied to a direct message with the same question, but I'm glad to share it here as well in case anyone else can benefit from it:
We have to be very careful when playing the numbers game. That is, just because something is believed by many, it does not automatically follow what they believe is true, for often it's not! This is true for religion, politics, science, philosophy and every idea.
Now, we can rejoice in that God has given us a means of testing people's ideas, so let's consider it in brief:
How can we be absolutely certain that an idea or teaching is from God?
We can compare it with the Bible, which is the Word of God, for this is what God's prophets, apostles and Jesus Himself explicitly teach throughout the written Word.
What about teachings that come from tradition? Are they from God?
Here we can make the following distinctions:
(1) If something is neither commanded nor forbidden by the Bible, we call it adiaphora. Here the Christian has freedom in Christ to either exercise it or refrain from exercising in whatever way best serves our neighbour.
(2) If someone claims that a doctrine is from God via tradition, we can test it against the Bible with the following:
1. Is the teaching commanded in the Bible?
2. Are there any promises connected to the teaching in the Bible?
3. Are there any examples of the teaching in the Bible?
If the answer to answer to the above is "no, no, and no", then we can be certain that the teaching is not from God, but is either man-made or a doctrine of demons.
The difference between (1) and (2) above is that (1) is not believed to be from God, but is a man-made thing we can exercise for the sake of good order. (2), however, is something supposed to be from God. So (1) concerns things that are not of divine right, but (2) concerns things that someone claims are by divine right.
So let's put this to the test with a couple of practical examples:
Celebrating Christmas
The Bible does not command nor forbid that we should celebrate Christmas. Here we have Christian freedom. However, we believe it's always good to reflect on Christ, so we celebrate Christ in our freedom.
The sign of the cross
Is it commanded by the Bible? No. Is it forbidden by the Bible? No. Again, here we have Christian freedom. No one is saying that this is a command from God, but rather, it's a man-made symbolic gesture to reflect our faith in Jesus who was crucified for our sins, and that we are baptised in His name.
Prayers to Mary, saints, and angels
1. Does the Bible command us to pray to Mary, saints, or angels? No.
2. Are there any promises in the Bible that Mary, saints, and angels can receive our prayers? No.
3. Are there any examples of anyone in the Bible praying to Mary, saints, or angels? No.
Conclusion: This doctrine is not from God, but is man-made or a doctrine of demons. For not only does it lack any command, promise, or example in God's Word, but it is also plainly against God's Word, for overwhelmingly throughout the Bible, we learn that prayers are only to be directed to God. He commands us to pray to Him, and He promises to hear our prayers, and every prayer by God's people in the Bible is directed to God alone.
Now, since the Roman Catholic Church claims that God speaks through their church, what they teach, believe, and confess ought to be consistent with the written Word, but often it's not. The example of prayers above is just one example of this. The Lutheran Church, however, makes no claim that God speaks to us through tradition, but is instead firmly rooted in God's Word alone, for we know that in it, we have the full assurance of God's Word. In the Bible, we have God's Law and Gospel and everything we need to know for our salvation. Regrettably, our Roman Catholic friends go far beyond what is written on many accounts.
So, with all of this in mind, we can simply ask: Which of the two church bodies are most consistent with the Bible? I think any honest person who knows the Scriptures would have to say the Lutheran Church. Now, if the question was who is the most consistent with the Bible and the Roman Catholic Holy Tradition, then, of course, it would be our Roman Catholic friends. But in this, we see that their fidelity is to the Bible AND what they understand to be a tradition from God. Whereas we are compelled to uphold what the Bible teaches and reject that which is contrary to it.
There is a lot more I can say about this, but this post is already very long! If you interested in the Church, I've written an article here that considers what the Church is:
The Church
Hope this helps! Blessings!