So as far as the issues in some of the protestant churches, I can begin naming them if you like. The Scripture warns us their are tares amongst the wheat, their are false teachers , wolves in sheeps' clothing , people with itching ears and those that will say Lord , Lord and find that Jesus rejects them, there will be a great falling away....People need to read their Bible's and stick to what is in it as a yardstick to measure if any churches or teachers are preaching the truth. Many people do not have a firm foundation in sound doctrine and many are ignorant or complacent. I speak equally about the unbiblical teachings in some denominations, but most of them, not all are at least giving the true gospel & teaching the essentials of Christianity. We cannot say that for the Rcc. It opposes God's word as the sole written authority.
As to the the RCC , institutionally it is in a category all to itself, it preaches a false gospel of faith plus works, the doctrine of purgatory, the Mary dogma, of Mary as the co-redemptrix, of prayers to sacred bones of dead rc pope declared saints. It combines pagan traditions with Christian, idolatry, worship of images of Mary of dead saints, it claims that it alone is "the one true church", it claims Apostolic succession, it goes on and on. It denies the sole sovereignty of the Holy God & justification is through Jesus Christ alone. It denies the sole authority of the scriptures & includes it's own traditions & writing as divine.
It means how can RC be saved when they are taught a false gospel? & so many other false teachings have been added & the usurping of Christ's authority? I have family members who are RC, they don't know what salvation is, they don't know what being born again means. They don't know that Jesus paid the cost of our sins by his blood. They don't know how to pray to GOD and asking in Jesus name. They have prayer cards with worship, homage & prayers to Mary. That is a problem. They don't know or believe the essentials of Christian faith. They are trusting in the Rcc to get them to heaven.