That could be argued, but Original Sin is believed to be the fate of all mankind, thanks to Adam's sin (barring divine intervention if anyone wants to believe in the Immaculate Conception), and all humans are descended from Adam. It's not something that's inherited genetically.
The reason those churches you mentioned say that Jesus was sinless is because he did not lose his divine nature by taking on human nature, and God does not and cannot know sin.
Personally I don’t believe that we inherited Adam’s sinful nature at all but instead that we are all created with the capability to sin and will at some point fall victim to sin because it’s just inevitable. Adam & Eve didn’t have to inherit their sinful nature from anyone they were created with it because they possessed free will which is what enabled them to sin in the first place. I like the way St Iranaeus explained it in Adversus Haereses.
1. Man has received the
knowledge of good and
evil. It is
good to
obey God, and to
believe in Him, and to keep His commandment, and this is the life of man; as not to
obey God is
evil, and this is his death. Since
God, therefore, gave [to man] such mental power (magnanimitatem) man
knew both the good of
obedience and the
evil of disobedience, that the eye of the
mind, receiving experience of both, may with judgment make choice of the better things; and that he may never become indolent or neglectful of God's command; and learning by experience that it is an
evil thing which deprives him of life, that is, disobedience to
God, may never attempt it at all, but that,
knowing that what preserves his life, namely,
obedience to
God, is
good, he may diligently keep it with all earnestness. Wherefore he has also had a twofold experience, possessing
knowledge of both kinds, that with discipline he may make choice of the better things. But how, if he had no
knowledge of the contrary, could he have had instruction in that which is
good? For there is thus a surer and an undoubted comprehension of matters submitted to us than the mere surmise arising from an opinion regarding them. For just as the tongue receives experience of sweet and bitter by means of tasting, and the eye discriminates between black and white by means of vision, and the ear recognises the distinctions of sounds by hearing; so also does the
mind, receiving through the experience of both the
knowledgeof what is
good, become more tenacious of its preservation, by acting in
obedience to God: in the first place, casting away, by means of repentance, disobedience, as being something disagreeable and nauseous; and afterwards coming to understand what it really is, that it is contrary to goodness and sweetness, so that the mind may never even attempt to taste disobedience to
God. But if any one do shun the
knowledge of both these kinds of things, and the twofold perception of
knowledge, he unawares divests himself of the character of a
human being.
2. How, then, shall he be a
God, who has not as yet been made a man? Or how can he be perfect who was but lately created? How, again, can he be
immortal, who in his mortal nature did not
obey his Maker? For it must be that you, at the outset, should hold the rank of a
man, and then afterwards partake of the
glory of
God. For you did not make
God, but God you. If, then, you are God's workmanship, await the hand of your Maker which creates everything in due time; in due time as far as you are concerned, whose creation is being carried out. Offer to Him your heart in a soft and tractable state, and preserve the form in which the Creator has fashioned you, having moisture in yourself, lest, by becoming hardened, you lose the impressions of His fingers. But by preserving the framework you shall ascend to that which is perfect, for the moist clay which is in you is hidden [there] by the workmanship of
God. His hand fashioned your substance; He will cover you over [too] within and without with pure gold and silver, and He will adorn you to such a degree, that even the King Himself shall have pleasure in your beauty. But if you, being obstinately hardened, reject the operation of His skill, and show yourself ungrateful towards Him, because you were created a [mere] man, by becoming thus ungrateful to
God, you have at once lost both His workmanship and life. For creation is an attribute of the goodness of God but to be created is that of
human nature. If then, you shall deliver up to Him what is yours, that is,
faith towards Him and subjection, you shall receive His handiwork, and shall be a perfect work of
God.
3. If, however, you will not
believe in Him, and will flee from His hands, the
cause of imperfection shall be in you who did not
obey, but not in Him who called [you]. For He commissioned [messengers] to call people to the marriage, but they who did not
obey Him deprived themselves of the royal supper.
Matthew 22:3, etc. The skill of
God, therefore, is not defective, for He has power of the stones to raise up children to
Abraham;
Matthew 3:9but the man who does not obtain it is the
causeto himself of his own imperfection. Nor, [in like manner], does the light fail because of those who have blinded themselves; but while it remains the same as ever, those who are [thus] blinded are involved in darkness through their own fault. The light does never enslave any one by necessity; nor, again, does God exercise compulsion upon any one unwilling to accept the exercise of His skill. Those
persons, therefore, who have
apostatized from the light given by the
Father, and transgressed the law of liberty, have done so through their own fault, since they have been created free agents, and possessed of power over themselves.
4. But
God, foreknowing all things, prepared fit habitations for both, kindly conferring that light which they desire on those who seek after the light of incorruption, and resort to it; but for the despisers and mockers who avoid and turn themselves away from this light, and who do, as it were, blind themselves, He has prepared darkness suitable to
personswho oppose the light, and He has inflicted an appropriate punishment upon those who try to avoid being subject to Him. Submission to
God is
eternal rest, so that they who shun the light have a place worthy of their flight; and those who fly from
eternal rest, have a habitation in accordance with their fleeing. Now, since all
good things are with
God, they who by their own determination fly from
God, do defraud themselves of all
good things; and having been [thus] defrauded of all
good things with respect to
God, they shall consequently fall under the just judgment of
God. For those
persons who shun rest shall
justly incur punishment, and those who avoid the light shall
justly dwell in darkness. For as in the case of this temporal light, those who shun it do deliver themselves over to darkness, so that they do themselves become the
cause to themselves that they are destitute of light, and do inhabit darkness; and, as I have already observed, the light is not the
cause of such an [unhappy] condition of
existence to them; so those who fly from the
eternal light of
God, which contains in itself all
good things, are themselves the
cause to themselves of their inhabiting
eternal darkness, destitute of all
goodthings, having become to themselves the
cause of [their consignment to] an abode of that nature.
St Iranaeus 170AD Adversus Haereses Book 4 Chapter 39
