I find it a little confusing. I don't know if I heard that Lutherans are pretty close and/or Old Anglicans (I may be totally off with the "Old" part but I'm trying to learn).
The question is very vague and imprecise. Also inaccurate. Closest in what sense. Orthodox, Lutherans, Old Anglicans, are all denominations and sects of Christianity and not religions. So perhaps you meant "Which denomination or sect is closest to catholic". Closest how? In spiritual guidance, belief, practice, social values ....etc?
The only true/real reason to belong to a church is because the church and the pastor teach & practice only what the Bible teaches. The Bible says "Earnestly contend for the faith that was delivered to the saints of old" Jude 3. The Bible describes this "faith" as the genuine faith of the Christian in Rev. 14:12 "Here is the patience of the saints. Here are they that keep the commandments of God and the faith of Jesus" The commandments and Jesus' teachings are the center of the church and must be upheld.A God of Love warns us with an everlasting Love that we have a choice to make. Will we stand on the Word of God (on safe ground) or will we follow the dictates of human beings?
Where can we find courageous pastors who fear not to call sin by its right name Paul urged the shepherds of his day to "Preach the word; be instant in season, out of season; reprove, rebuke, exhort with all longsuffering and doctrine." Then, he made this astounding prediction: "For the time will come when they will not endure sound doctrine; but after their own lusts shall they heap to themselves teachers, having itching ears; And they shall turn away their ears from the truth, and shall be turned unto fables." 2 Timothy 4:2-4.
These words are being fulfilled before our very eyes. Fables are being taught, doctrinal messages are drying up, and millions are turning from truth to pleasing platitudes. Any sermon that demands obedience or self-denial is rejected out of hand as legalistic and judgmental. The voice of rebuke is seldom heard, and pointed preaching which identifies the biblical antichrist is looked upon as harsh. Have we overdrawn the picture I don't believe any careful observer of the religious scene would contend that we have. Surely Satan is working harder inside the church than he is on the outside, and his plan is to produce the most clever counterfeit of truth that has ever existed. By creating a diabolical parallel system of doctrinal error within the church itself, he has already led millions into a false worship. The nefarious plot was recognized and exposed by the Holy Spirit shortly before the great deceiver began to implement the major elements of his plan in the post-apostolic church.
Amazingly, some of the most prominent doctrines of Protestantism today are not found in the Bible at all. They have been brought into the Protestant churches by the mother church of Rome, who received them from paganism. A few of these false teachings are that:
A. The law of God has been amended or repealed.
God's law can never be changed or repealed (Luke 16:17).
B. The soul is immortal.
The Bible mentions "soul" and "spirit" 1,700 times. Not once is either referred to as immortal. People are mortal (Job 4:17), and none receive immortality until Jesus' second advent (1 Corinthians 15:51-54).
C. Sinners burn eternally in hell.
The Bible teaches that sinners will be completely consumed (put out of existence), both soul and body, in the fire (Matthew 10:28). An eternal hell of torment is not taught in the Bible.
D. Baptism by immersion is not necessary.
Baptism by immersion is the only baptism recognized by Scripture.
E. Sunday is God's holy day.
The Bible teaches, without question, that God's holy day is the seventh-day Sabbath--Saturday
Note: These false teachings, once believed, tend to bring "confusion" (which is what the term "Babylon" literally means) and make understanding Scripture much more difficult.
A Sobering Thought
It's sobering to think that some might unknowingly be drinking Babylon's wine. Perhaps this is all new to you. If so, please ask God to guide you (Matthew 7:7). Then search the Scriptures to see if these things are so (Acts 17:11). Promise that you will follow where Jesus leads, and He will not permit you to end up in error (John 7:17).