>>But allowing states to regulate abortion, for example, would be denying the People the right to get one should they so choose<<
I think you're wrong.
The Ninth cannot mean that individuals can perform any action not forbidden by the Constitution.
It also can't mean that anything that the Congress cannot legislate on must be legal.
The rights and powers of the People have expression in the legislatures of the several states (scary, ain't it?).
States have broad powers to legislate in areas denied to Congress by the Tenth-and these legislative acts are manifestations of the retained rights referred to by Nine.
I think your "'The rights of the People' really means the 'Right of the State to regulate the People'" argument is one interpretation of what is written, but not the only one.
This is the "wiggle room" clause that the lawyers who wrote the Constitution put in to address things that they could not foresee. It is poorly written. They should have been much more specific and stated that federal courts could not pass on the legality of state laws to regulate rights not given to the feds in the Constitution if that's what they meant.
The way it is now, we are left to argue what a right of the People is and what a right of the State to regulate the People is, and who gets to decide if any of it is governed by the 9th.