This “trendy little epithet” that you so cheekily ignore was given to Paul, by Christ. It gets you on the other side of the Cross.
And Jesus went throughout all the cities and villages, teaching in their synagogues and proclaiming the gospel of the kingdom and healing every disease and every affliction. (Matt. 9:35)
You seem to be applying "Gospel of the Kingdom" to the godless Catholics.... perhaps I am mistaken in that perception?