Many Christians think about the gospel as merely the entry gate into Christianity. It’s a gate opened with an invitation to faith (“Do you confess you are a sinner and accept Jesus as your Lord and Savior?”) and walked through with a prayer of salvation.
There is truth in that understanding of the gospel. But only about as much truth as believing that the earth is a sphere or that Albert Einstein was human. They are correct statements, but little of reality has been stated. There’s so much more we can (and should) say.