You should read the U.S. Constitution, Article III, Section 2, Clause 2. The second sentence therein states: "In all the other Cases before mentioned, the supreme Court shall have appellate Jurisdiction, both as to Law and Fact, with such Exceptions, and under such Regulations as the Congress shall make."
Thus, the Supreme Court is an appellate court subject to restrictions imposed by Congress--by statute, not amendment. The only areas in which Congress can not interfere (without amendment) are those few areas mentioned in the first sentence of the clause: cases affecting ambassadors, public ministers and consuls, and where a state is a party. That gives Congress an enormous amount of authority over the Court that they have been too timid to use.
Clause one supercedes and gives both primary jurisdiction and the fundamental powers. They are given w/o exception, or limit, including infringement by Congress. Clause 2 involves other powers and tasks.