In listening to the Church regarding faith and morals, Catholics believe we are not listening to just "the opinions of a flawed person", but to Christ Himself. Certainly a person should seek and listen to the inner guidance of God within but, as you have rightly observed, we are all flawed, so there is a risk our SUBJECTIVE judgement and discernment can come to erroneous conclusions regarding faith and morals. God, in His infinite Love and Mercy gave us the Church, which He promised to protect always from "Hades" - the lies and errors of the Evil One - so that humanity would always have a sure repository of Truth for the good, guidance and salvation of all.

Matthew 7:24

Everyone then who hears these words of mine and does them will be like a wise man who built his house on the ROCK.

Matthew 16:18

And I tell you that you are Peter, and on this ROCK I will build my church, and the gates of Hades will not overcome it.