the tanakh is very clear that the dross are israel
No. You need to read the whole story.
The House of Israel ( as Constrasted with the House of Jacob ) are dross to the LORD at that time in that place, because... they mixed with the others and adopted their practices.
Go back chapter 20:
And say to them, Thus says the Lord God; In the day when I chose Israel, and raised my hand to the seed of the house of Jacob, and made myself known to them in the land of Egypt, when I raised my hand to them, saying, I am the Lord your God;
See that ^^ there is a difference.
But the
house of Israel rebelled against me in the wilderness; they walked not in my statutes, and they despised my judgments, by whose observance man shall live; and my sabbaths they greatly profaned; then I said, I would pour out my fury upon them in the wilderness, to consume them.
Who is that??? In the wilderness? They are NOT the House of Jacob...
And the mixed multitude that was among them had a strong craving; and the people of Israel also wept again, and said, Who shall give us meat to eat?
Notice, Israel was influenced by the mixed multitude. Who are they?
And the people of Israel journeyed from Rameses to Succoth, about six hundred thousand on foot, who were men, beside children. And a mixed multitude went up also with them; and flocks, and herds, and very many cattle.
The mixed multitude are the egyptians who wandered with them and mixed with them. The "House of Israel" is influences by them from the very begining
Again, the culture of egypt.
Blah-blah-blah...
You said that the whole purpose of the temple is for guilt. You were wrong. The egyptians considered pharaoh a god. They're not Jewish. Case closed.