If at any time the distinctions between clean and unclean meats had ceased to exist, shouldn't that have been made clear in the Bible through the example of God's servants?
On the contrary, well into the time of the early Church we find Christ's followers scrupulously avoiding eating animal flesh that God had revealed as being unclean (Acts 10:14 Acts 10:14But Peter said, Not so, Lord; for I have never eaten any thing that is common or unclean.
American King James Version×; Acts 11:8 Acts 11:8But I said, Not so, Lord: for nothing common or unclean has at any time entered into my mouth.
American King James Version×). Prophecies of the time of the end make the same distinctions (Revelation 18:2 Revelation 18:2And he cried mightily with a strong voice, saying, Babylon the great is fallen, is fallen, and is become the habitation of devils, and the hold of every foul spirit, and a cage of every unclean and hateful bird.
American King James Version×; Isaiah 66:15-17 Isaiah 66:15-17  For, behold, the LORD will come with fire, and with his chariots like a whirlwind, to render his anger with fury, and his rebuke with flames of fire.  For by fire and by his sword will the LORD plead with all flesh: and the slain of the LORD shall be many.  They that sanctify themselves, and purify themselves in the gardens behind one tree in the middle, eating swine's flesh, and the abomination, and the mouse, shall be consumed together, said the LORD.
American King James Version×).
But there's more to the matter than diet. A thorough study of the Bible helps us understand other dimensions to the significance of the distinctions between clean and unclean meats.
God's Word describes the flesh of unclean animals as an "abomination" (Leviticus 11:10-13 Leviticus 11:10-13  And all that have not fins and scales in the seas, and in the rivers, of all that move in the waters, and of any living thing which is in the waters, they shall be an abomination to you:
 They shall be even an abomination to you; you shall not eat of their flesh, but you shall have their carcasses in abomination.
 Whatever has no fins nor scales in the waters, that shall be an abomination to you.
 And these are they which you shall have in abomination among the fowls; they shall not be eaten, they are an abomination: the eagle, and the ossifrage, and the ospray,
American King James Version×; Leviticus 11:20-23 Leviticus 11:20-23  All fowls that creep, going on all four, shall be an abomination to you.  Yet these may you eat of every flying creeping thing that goes on all four, which have legs above their feet, to leap with on the earth;  Even these of them you may eat; the locust after his kind, and the bald locust after his kind, and the beetle after his kind, and the grasshopper after his kind.  But all other flying creeping things, which have four feet, shall be an abomination to you.
American King James Version×; Leviticus 11:41-42 Leviticus 11:41-42  And every creeping thing that creeps on the earth shall be an abomination; it shall not be eaten.  Whatever goes on the belly, and whatever goes on all four, or whatever has more feet among all creeping things that creep on the earth, them you shall not eat; for they are an abomination.
American King James Version×) and "detestable" (Deuteronomy 14:3 Deuteronomy 14:3You shall not eat any abominable thing.
American King James Version×)—and in that light we are warned against consuming such meat (Leviticus 11:43 Leviticus 11:43You shall not make yourselves abominable with any creeping thing that creeps, neither shall you make yourselves unclean with them, that you should be defiled thereby.
American King James Version×). Strong language, but the lesson is that we need to accept all aspects of the Bible, including the basic food laws in Leviticus 11 and Deuteronomy 14.
In instituting the sacrificial system for ancient Israel, God commanded many specific sacrifices involving animals. Nowhere, however, does He command or allow the sacrifice of an unclean animal, nor is there a record of any of God's servants ever sacrificing such an animal to Him. Such a sacrifice would have joined the holy with that which God had designated unclean and defiled. It would have been simply unthinkable to a true servant of God because it would have been an affront to the Creator Himself.