John 17:17 Sanctify them in the truth; your word is truth.
Ephesians 1:13-14 In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit, who is the guarantee of our inheritance until we acquire possession of it, to the praise of his glory.
2 Timothy 2:15 Do your best to present yourself to God as one approved, a worker who has no need to be ashamed, rightly handling the word of truth.
Truth is not relative and is not subject to change. If someone changes it, it's no longer true.
Catholic doctrine has changed much over the years, often teaching contradictory things. Both CANNOT be true.
And if you had concrete examples of this you would have cited them.