Figs from a thistle?

The falling away stated by Paul in Galatians (Galatians 5: 4) is also stated in Hebrews 6: 4-6 (Jews falling back to law, requiring a second sacrifice) and has been underway since Jerome translated metanoia as do penance. The entire ship is off course by just enough creating a thorn bush in place of a vine.  “Abide in the vine.” People don’t “pick grapes from a thorn bush or figs from a thistle.”  John 16: 27.