Thoughts on Congress Rendering the SCOTUS Useless

Question: What is the purpose of the Supreme Court of the United States?

Answer: To rule on the constitutionality of laws passed by the Congress.

Question: What would be the effect of Congress passing a law that bars the SCOTUS from ruling on matters of whether religious expression violates the Constitution?

Answer: Effectively rendering the SCOTUS powerless regarding certain matters of constitutionality.

Of course, that's just what conservative legislators want to do. They want to take the Supreme Court out of the picture. I wonder how they'd feel if the SCOTUS ruled that conservative legislators who try to outlaw the SCOTUS are unconstitutional and therefore banned from the lawmaking process and ever being elected again.

Consevative lawmakers to the Supreme Court: "We don't like you. You shut up!"

So...what if Congress passed a law saying that the SCOTUS could no longer rule on Constitutional matters -- which is, by the way, the Court's job. Can Congress pass laws effectively neutering the SCOTUS? If they can, they could outlaw the SCOTUS before it could ever rule on whether or not such a law was constitutional!

I'm sure, in my infinite wisdom of Constitutional law, I'm missing something. And so must conservative legislators who are trying to bar the SCOTUS from ruling on particular Constitutional matters.