It was a brilliant solution. It was a combination of a democracy (The House) which addressed the concerns of the people and an oligarchy (The Senate) which addressed the concerns of the States. ... and was totally undermined by the adoption of the 17th Amendment.
The House, with representation by population favored the large States; while the Senate, with each State having two representatives, favored the smaller States.
About the 9th and 10th Amendments. AMENDMENT IX to the Constitution of the United States: The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.