Several things to notice about the 144,000.
They stand on Mt Zion with the lamb of God
And I saw and beheld the lamb standing upon Mount Zion, and with him one hundred, forty-four thousands having his name and his father's name written upon their foreheads. Revelation 14:1
Mt Zion is the throne of God, so we can reasonably conclude that the 144,000 are collectively referred to as the manchild who is caught up to the throne of God and who will shepherd all nations with an iron staff
And she brought forth a man child, who was to shepherd all nations with an iron staff: and her child was caught up unto God, and [to] his throne. Revelation 12:5
Shepherding all nations with an iron staff is a reward given to those who in the spirit of the fear of God guard his works and overcome the world.
And to the one conquering and guarding my works until the end, I will give authority over the peoples. And he will shepherd them with an iron staff, as the clay vessels are shattered, as I have received from my father. Revelation 2:26-27
Since there have been many overcomers throughout history, it seems reasonable to think that the 144,000 are a select group for a select time who are chosen (sealed), not based on genealogy or physical circumcision, but on obedience to the lamb of God. Geneaology and physical circumcision really mean nothing to God since Christ fulfilled everything pertaining to the promises to Abraham and the law and prophets. Physical circumcision means nothing and from stones God can make children of Abraham, because Abraham's children are of faith.
Circumcision is nothing, and uncircumcision is nothing, but the keeping of the commandments of God. 1 Corinthians 7:19
Bring forth therefore fruits worthy of repentance, and begin not to say within yourselves, We have Abraham to [our] father: for I say unto you, That God is able of these stones to raise up children unto Abraham. Luke 3:8
Know ye therefore that they which are of faith, the same are the children of Abraham. Galatians 3:7
So if the children of Abraham are of faith and being a Jew (judean) is an inward matter of the heart, it's not a stretch to think that the 144,000 are chosen by God, not based on genealogy or physical circumcision, but on spiritual obedience.
For he is not a Jew [Judean], which is one outwardly; neither [is that] circumcision, which is outward in the flesh: But he [is] a Jew [Judean], which is one inwardly; and circumcision [is that] of the heart, in the spirit, [and] not in the letter; whose praise [is] not of men, but of God. Romans 2:28-29