The people in Matthew 7 appeal to works they performed in Jesus’ name. He answers, “I never knew you.” He does not say they once belonged and then lost it. Genuine believers already belong to him. “I never knew you” already secures them. The warning calls those who do belong to get the heart right and prioritize the main thing. It does not threaten their final standing.
1 John sets a high ideal and then says that if anyone does sin, we have an advocate with the Father (1 John 2:1–2). Paul forbids continuing in sin (Romans 6), describes the ongoing struggle (Romans 7), and declares no condemnation for those in Christ (Romans 8:1). Fruit is the right way to live. It is not the condition that places a person in Christ or keeps them there. Once saved always saved.
Performing cleanliness for an audience is not the same as belonging. I am a Christian and an artist. I am also a sinner. I am not going to pretend otherwise. Readers can examine the passages. They can disagree. The claim is narrow: belonging and performance are distinct.