Hebrews 6:4–6 doesn’t overturn those texts—it explains false profession, not loss of true salvation.
The people there are “partakers” of external privileges (light, taste, powers), but the writer never says they are regenerated, justified, or sealed; when they fall away, he calls it “impossible…to renew them again unto repentance,” which matches apostasy, not a justified man becoming unjustified.
Scripture is explicit: all the Father gives to the Son come and are kept (John 6:37–39), Christ’s sheep “shall never perish” and “no man is able to pluck them” from His and the Father’s hand (John 10:28–29), the justified are unbreakably carried from foreknowledge to glorification (Rom 8:29–30), and the elect are “kept by the power of God” (1 Pet 1:5).
When some depart, John says they “went out from us, but they were not of us” (1 John 2:19), and Hebrews itself defines the real believer as one who “holds the beginning of our confidence stedfast unto the end” (Heb 3:14).
So the principle stands: the elect never lose salvation; Hebrews 6 describes those who were near the gospel and its gifts, yet never truly united to Christ.