Thou shall not murder, yes indeed. Both Catholics and Jews provide for a person to disqualify him/ herself from continued affiliation for the most serious transgressions But there’s no mechanism announcing that. Both faiths also provide for excommunication by the clergy - which is visible-but neither wants, does it very often. The result is as you say— A bunch of apostates running around claiming they’re still affiliated. Including a few in the clergy itself ( sane for some protestant churches) It’s false advertising
A good start would be others telling them “you’re NOT (said religion) if you believe in abortion. You’re just not.”
And the larger community ostracizing them from the church.
Sounds like not the Christian thing to do? It actually is.
Jesus accepted sinners but not if they were gonna keep sinning with no remorse and actual pride of their sin.
And the clergy...the Catholic Church may need another schism..since our pope is a communist!!!