….no mechanism to decide.
I can’t speak for other religions, but for Christians, actually there is… Jesus was aware that interpretations would be profuse, so he cut through all that, by stating that actions would help one to decide: John 13:35 … love would be a noticeable feature of genuine Christians. Matthew 5:44 takes that love even further. When God puts His spirit on either an individual or a group, there are “fruitages” that one should expect to see. That others can see / observe. Galatians 5:22-23.
This eliminates the need to search / examine all doctrines. As you correctly intimated, such a search would never end!
Take care!