By AD70, those enemies were judged, the Old Covenant ended, and the full visible reign of Christ was revealed. So when Hebrews was written, it was true to say, "we do not yet see all things subjected", but that has since changed.

Hebrews 2:8 says, "You have put all things in subjection under His feet." This shows Christ had already been given full authority (Matthew 28:18), but the writer adds, "we do not yet see all things subjected to Him." Why? Because at the time Hebrews was written, the Old Covenant system was still active, the temple was still standing, and rebellious Israel had not yet been judged.

Though Christ reigned from heaven, the full manifestation of that reign was still unfolding. His enemies, chiefly apostate Jerusalem, had not yet been made His footstool (Psalm 110:1). But once the judgment came in AD70, the last obstacle to His visible reign was removed. What they did not yet see then, we now see in full: the Kingdom is established, the Old has passed away, and all things have been placed under His feet.