Disclaimer: I do not speak for any sect.
I would not recognize a page in the Bible that doesn't contain some screeds against Jews for being Jews. I'm not just talking about the NT, but in the OT. Stephen's screed is a typical example of "Judean bashing." Here Isaiah complains about the futility and mockery of the Temple and the whole sacrificial system:
[Isa 66:1-4 NKJV]  Thus says the LORD: "Heaven [is] My throne, And earth [is] My footstool. Where [is] the house that you will build Me? And where [is] the place of My rest?  For all those [things] My hand has made, And all those [things] exist," Says the LORD. "But on this [one] will I look: On [him who is] poor and of a contrite spirit, And who trembles at My word.  "He who kills a bull [is as if] he slays a man; He who sacrifices a lamb, [as if] he breaks a dog's neck; He who offers a grain offering, [as if he offers] swine's blood; He who burns incense, [as if] he blesses an idol. Just as they have chosen their own ways, And their soul delights in their abominations,  So will I choose their delusions, And bring their fears on them; Because, when I called, no one answered, When I spoke they did not hear; But they did evil before My eyes, And chose [that] in which I do not delight."
He says that if they want forgiveness, they don't need to offer an animal, just ask with a contrite heart:
[Psa 51:14-19 NKJV]  Deliver me from the guilt of bloodshed, O God, The God of my salvation, [And] my tongue shall sing aloud of Your righteousness.  O Lord, open my lips, And my mouth shall show forth Your praise.  For You do not desire sacrifice, or else I would give [it]; You do not delight in burnt offering.  The sacrifices of God [are] a broken spirit, A broken and a contrite heart--These, O God, You will not despise.  Do good in Your good pleasure to Zion; Build the walls of Jerusalem.  Then You shall be pleased with the sacrifices of righteousness, With burnt offering and whole burnt offering; Then they shall offer bulls on Your altar.
The Temple Not Made With Hands is the New Jerusalem, the Lambkin's "Bride-City." It is not just a fancier building, but one composed of living stones:
[1Pe 2:4-6, 9-10 NKJV]  Coming to Him [as to] a living stone, rejected indeed by men, but chosen by God [and] precious,  you also, as living stones, are being built up a spiritual house, a holy priesthood, to offer up spiritual sacrifices acceptable to God through Jesus Christ.  Therefore it is also contained in the Scripture, "Behold, I lay in Zion A chief cornerstone, elect, precious, And he who believes on Him will by no means be put to shame." ...  But you [are] a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light;  who once [were] not a people but [are] now the people of God, who had not obtained mercy but now have obtained mercy.
[Eph 2:19-22 CSB]  So, then, you are no longer foreigners and strangers, but fellow citizens with the saints, and members of God's household,  built on the foundation of the apostles and prophets, with Christ Jesus himself as the cornerstone.  In him the whole building, being put together, grows into a holy temple in the Lord.  In him you are also being built together for God's dwelling in the Spirit.
[Rev 21:22-27 NKJV]  But I saw no temple in it, for the Lord God Almighty and the Lamb are its temple.  The city had no need of the sun or of the moon to shine in it, for the glory of God illuminated it. The Lamb [is] its light.  And the nations of those who are saved shall walk in its light, and the kings of the earth bring their glory and honor into it.  Its gates shall not be shut at all by day (there shall be no night there).  And they shall bring the glory and the honor of the nations into it.  But there shall by no means enter it anything that defiles, or causes an abomination or a lie, but only those who are written in the Lamb's Book of Life.
And note that the building was already on the land, surrounded by various sinners, and was adding more and more stones to the Temple, and the nations are bringing tribute.
The difference between Cain's sacrifice and Abel's sacrifice was the state of their heart, not type of gift (although that might have provided evidence about the state of their hearts).
His point, then, is that their hearts are not right, they are murderers and they don't keep the law, and the sacrificial system won't help them.