Well even reading and studying the Bible for yourself can still lead directly to theological error. A great many denominations which have dubious doctrines, like the Mormons and Jehovah’s Witnesses and the non-trinitarian Adventists, resulted from people reading the Bible*
This is why ecclesiastical authority is so important. And to verify which churches are teaching doctrine correctly, well, many people are not called to do that, but some people, including myself, were put in positions to have to study that. And the easiest way is to study the history and the doctrines of the early church and then look at the denominations in existence today, and see which churches are closest to the Patristic church of the first few centuries of Christianity, before certain controversial events such as the Chalcedonian Schism, the adoption of the filiioque, the East-West schism between the Orthodox and Catholics following a Roman Pope excommunicating the Patriarch of Constantinople, which was hardened by acts of violence towards Eastern Christians in the Crusades.
*usually the KJV as it was most widespread and lacked the doctrinal commentaries of the Geneva Bible and the Challoner Douai Rheims (by design, because it was needed by the Church of England, whose members at the turn of the 17th century ranged from Puritans to extremely high church Anglo-Papalists who would be members of the Roman Catholic Church except for the fact that it was illegal, and the Elizabethan Settlement that had unified these diverse groups in the Church of England essentially required that doctrinal commentaries such as those used by the Calvinists in the Geneva Bible and the Roman Catholics in the Douai Rheims be not included). However any scriptural version, even one with a commentary, is at risk of being misunderstood.