>Congress is the ONLY branch of the government which gets to shape the boundaries of constitutional law.
Yeah, no. Not even close. Are you familiar with Miranda, Brown v. Board, Obergefell and dozens or hundreds of others? These are all the supreme court shaping the boundaries of constitutional law. Congress has zero power to intefere here. If Congress passed a law trying to outlaw gay marriage tomorrow, it would be unconstitutional and unenforceable immediately.
You say it yourself in your second paragraph: Congress has plenary power to shape the boundaries of constitutional law via amendments.
No, I didn't say that. Congress does not have "plenary power" (not a single actor in US government has plenary power). Constitutional amendments require approval by states, so if you think I was saying congress had plenary power over anything, you misread.
>he judiciary only has power when the legislature has not spoken, and that power should, theoretically, be constrained to mapping the smallest contours of the constitution because delineating the shape of the boundary is Congress's domain (some would say it is their most important duty, which they have neglected for the past half century).
Not true at all. The Supreme Court can rule any legislative act of congress unconstitutional. Congress can make whatever law it wants and Scotus can say "nope". I love that someone who doesn't know about Marbury v. Madison is attempting to lecture me on constitutional law.